Add method to sk_gpu_test::TestContext to automatically restore the previous context.

The motivation for this is to allow a GM to create a GL context, do some some work in it, and then return to the context that was set when it was invoked.

Change-Id: Ie8496072a10f8f3ff36a08889e593a6ca961b61a
Reviewed-on: https://skia-review.googlesource.com/70720
Commit-Queue: Brian Salomon <bsalomon@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>

10 files changed, 192 insertions, 19 deletions

diff --git a/tools/gpu/gl/angle/GLTestContext_angle.cpp b/tools/gpu/gl/angle/GLTestContext_angle.cpp
index 52cc5128da..3b55c40bac 100644
--- a/tools/gpu/gl/angle/GLTestContext_angle.cpp
+++ b/tools/gpu/gl/angle/GLTestContext_angle.cpp
@@ -34,6 +34,16 @@ struct Libs {
     void* fEGLLib;
 };
 
+std::function<void()> context_restorer() {
+    auto display = eglGetCurrentDisplay();
+    auto dsurface = eglGetCurrentSurface(EGL_DRAW);
+    auto rsurface = eglGetCurrentSurface(EGL_READ);
+    auto context = eglGetCurrentContext();
+    return [display, dsurface, rsurface, context] {
+        eglMakeCurrent(display, dsurface, rsurface, context);
+    };
+}
+
 static GrGLFuncPtr angle_get_gl_proc(void* ctx, const char name[]) {
     const Libs* libs = reinterpret_cast<const Libs*>(ctx);
     GrGLFuncPtr proc = (GrGLFuncPtr) GetProcedureAddress(libs->fGLLib, name);
@@ -87,6 +97,7 @@ private:
     void destroyGLContext();
 
     void onPlatformMakeCurrent() const override;
+    std::function<void()> onPlatformGetAutoContextRestore() const override;
     void onPlatformSwapBuffers() const override;
     GrGLFuncPtr onPlatformGetProcAddress(const char* name) const override;
 
@@ -214,6 +225,7 @@ ANGLEGLContext::ANGLEGLContext(ANGLEBackend type, ANGLEContextVersion version,
 
     fSurface = eglCreatePbufferSurface(fDisplay, surfaceConfig, surfaceAttribs);
 
+    SkScopeExit restorer(context_restorer());
     if (!eglMakeCurrent(fDisplay, fSurface, fSurface, fContext)) {
         SkDebugf("Could not set the context.");
         this->destroyGLContext();
@@ -320,7 +332,10 @@ std::unique_ptr<sk_gpu_test::GLTestContext> ANGLEGLContext::makeNew() const {
 
 void ANGLEGLContext::destroyGLContext() {
     if (EGL_NO_DISPLAY != fDisplay) {
-        eglMakeCurrent(fDisplay, EGL_NO_SURFACE, EGL_NO_SURFACE, EGL_NO_CONTEXT);
+        if (eglGetCurrentContext() == fContext) {
+            // This will ensure that the context is immediately deleted.
+            eglMakeCurrent(fDisplay, EGL_NO_SURFACE, EGL_NO_SURFACE, EGL_NO_CONTEXT);
+        }
 
         if (EGL_NO_CONTEXT != fContext) {
             eglDestroyContext(fDisplay, fContext);
@@ -355,6 +370,13 @@ void ANGLEGLContext::onPlatformMakeCurrent() const {
     }
 }
 
+std::function<void()> ANGLEGLContext::onPlatformGetAutoContextRestore() const {
+    if (eglGetCurrentContext() == fContext) {
+        return nullptr;
+    }
+    return context_restorer();
+}
+
 void ANGLEGLContext::onPlatformSwapBuffers() const {
     if (!eglSwapBuffers(fDisplay, fSurface)) {
         SkDebugf("Could not complete eglSwapBuffers.\n");
diff --git a/tools/gpu/gl/command_buffer/GLTestContext_command_buffer.cpp b/tools/gpu/gl/command_buffer/GLTestContext_command_buffer.cpp
index 54845fc28b..18e150611a 100644
--- a/tools/gpu/gl/command_buffer/GLTestContext_command_buffer.cpp
+++ b/tools/gpu/gl/command_buffer/GLTestContext_command_buffer.cpp
@@ -25,6 +25,7 @@ typedef void* EGLNativeDisplayType;
 typedef void* EGLNativeWindowType;
 typedef void (*__eglMustCastToProperFunctionPointerType)(void);
 #define EGL_FALSE 0
+#define EGL_TRUE 1
 #define EGL_OPENGL_ES2_BIT 0x0004
 #define EGL_CONTEXT_CLIENT_VERSION 0x3098
 #define EGL_NO_SURFACE ((EGLSurface)0)
@@ -45,6 +46,8 @@ typedef void (*__eglMustCastToProperFunctionPointerType)(void);
 #define EGL_NONE 0x3038
 #define EGL_WIDTH 0x3057
 #define EGL_HEIGHT 0x3056
+#define EGL_DRAW 0x3059
+#define EGL_READ 0x305A
 
 typedef EGLDisplay (*GetDisplayProc)(EGLNativeDisplayType display_id);
 typedef EGLBoolean (*InitializeProc)(EGLDisplay dpy, EGLint *major, EGLint *minor);
@@ -77,6 +80,37 @@ static GetProcAddressProc gfGetProcAddress = nullptr;
 static void* gLibrary = nullptr;
 static bool gfFunctionsLoadedSuccessfully = false;
 
+// The command buffer does not correctly implement eglGetCurrent. It always returns EGL_NO_<foo>.
+// So we implement them ourselves and hook eglMakeCurrent to store the current values in TLS.
+thread_local EGLDisplay gCurrDisplay = EGL_NO_DISPLAY;
+thread_local EGLSurface gCurrReadSurface = EGL_NO_SURFACE;
+thread_local EGLSurface gCurrDrawSurface = EGL_NO_SURFACE;
+thread_local EGLContext gCurrContext = EGL_NO_CONTEXT;
+
+EGLDisplay fakeGetCurrentDisplay() { return gCurrDisplay; }
+EGLSurface fakeGetCurrentSurface(EGLint readdraw) {
+    switch (readdraw) {
+        case EGL_DRAW:
+            return gCurrDrawSurface;
+        case EGL_READ:
+            return gCurrReadSurface;
+        default:
+            return EGL_NO_SURFACE;
+    }
+}
+EGLContext fakeGetCurrentContext() { return gCurrContext; }
+
+EGLBoolean hookedMakeCurrent(EGLDisplay display, EGLSurface draw, EGLSurface read, EGLContext ctx) {
+    if (gfFunctionsLoadedSuccessfully && EGL_TRUE == gfMakeCurrent(display, draw, read, ctx)) {
+        gCurrDisplay = display;
+        gCurrDrawSurface = draw;
+        gCurrReadSurface = read;
+        gCurrContext = ctx;
+        return EGL_TRUE;
+    }
+    return EGL_FALSE;
+}
+
 namespace {
 static void load_command_buffer_functions() {
     if (!gLibrary) {
@@ -104,12 +138,11 @@ static void load_command_buffer_functions() {
             gfSwapBuffers = (SwapBuffersProc)GetProcedureAddress(gLibrary, "eglSwapBuffers");
             gfGetProcAddress = (GetProcAddressProc)GetProcedureAddress(gLibrary, "eglGetProcAddress");
 
-            gfFunctionsLoadedSuccessfully = gfGetDisplay && gfInitialize && gfTerminate &&
-                                            gfChooseConfig && gfCreateWindowSurface &&
-                                            gfCreatePbufferSurface && gfDestroySurface &&
-                                            gfCreateContext && gfDestroyContext && gfMakeCurrent &&
-                                            gfSwapBuffers && gfGetProcAddress;
-
+            gfFunctionsLoadedSuccessfully =
+                    gfGetDisplay && gfInitialize && gfTerminate && gfChooseConfig &&
+                    gfCreateWindowSurface && gfCreatePbufferSurface && gfDestroySurface &&
+                    gfCreateContext && gfDestroyContext && gfMakeCurrent && gfSwapBuffers &&
+                    gfGetProcAddress;
         }
     }
 }
@@ -134,6 +167,19 @@ static const GrGLInterface* create_command_buffer_interface() {
     return GrGLAssembleGLESInterface(gLibrary, command_buffer_get_gl_proc);
 }
 
+std::function<void()> context_restorer() {
+    if (!gfFunctionsLoadedSuccessfully) {
+        return nullptr;
+    }
+    auto display = fakeGetCurrentDisplay();
+    auto dsurface = fakeGetCurrentSurface(EGL_DRAW);
+    auto rsurface = fakeGetCurrentSurface(EGL_READ);
+    auto context = fakeGetCurrentContext();
+    return [display, dsurface, rsurface, context] {
+        hookedMakeCurrent(display, dsurface, rsurface, context);
+    };
+}
+
 }  // anonymous namespace
 
 namespace sk_gpu_test {
@@ -204,7 +250,8 @@ CommandBufferGLTestContext::CommandBufferGLTestContext(CommandBufferGLTestContex
         return;
     }
 
-    if (!gfMakeCurrent(fDisplay, fSurface, fSurface, fContext)) {
+    SkScopeExit restorer(context_restorer());
+    if (!hookedMakeCurrent(fDisplay, fSurface, fSurface, fContext)) {
         SkDebugf("Command Buffer: Could not make EGL context current.\n");
         this->destroyGLContext();
         return;
@@ -237,15 +284,19 @@ void CommandBufferGLTestContext::destroyGLContext() {
     if (EGL_NO_DISPLAY == fDisplay) {
         return;
     }
+    bool wasCurrent = false;
     if (EGL_NO_CONTEXT != fContext) {
+        wasCurrent = fakeGetCurrentContext() == fContext;
         gfDestroyContext(fDisplay, fContext);
         fContext = EGL_NO_CONTEXT;
     }
-    // Call MakeCurrent after destroying the context, so that the EGL implementation knows that
-    // the context is not used anymore after it is released from being current.  This way
-    // command buffer does not need to abandon the context before destruction, and no
-    // client-side errors are printed.
-    gfMakeCurrent(fDisplay, EGL_NO_SURFACE, EGL_NO_SURFACE, EGL_NO_CONTEXT);
+    if (wasCurrent) {
+        // Call MakeCurrent after destroying the context, so that the EGL implementation knows that
+        // the context is not used anymore after it is released from being current.This way the
+        // command buffer does not need to abandon the context before destruction, and no
+        // client-side errors are printed.
+        hookedMakeCurrent(fDisplay, EGL_NO_SURFACE, EGL_NO_SURFACE, EGL_NO_CONTEXT);
+    }
 
     if (EGL_NO_SURFACE != fSurface) {
         gfDestroySurface(fDisplay, fSurface);
@@ -258,11 +309,18 @@ void CommandBufferGLTestContext::onPlatformMakeCurrent() const {
     if (!gfFunctionsLoadedSuccessfully) {
         return;
     }
-    if (!gfMakeCurrent(fDisplay, fSurface, fSurface, fContext)) {
+    if (!hookedMakeCurrent(fDisplay, fSurface, fSurface, fContext)) {
         SkDebugf("Command Buffer: Could not make EGL context current.\n");
     }
 }
 
+std::function<void()> CommandBufferGLTestContext::onPlatformGetAutoContextRestore() const {
+    if (!gfFunctionsLoadedSuccessfully || fakeGetCurrentContext() == fContext) {
+        return nullptr;
+    }
+    return context_restorer();
+}
+
 void CommandBufferGLTestContext::onPlatformSwapBuffers() const {
     if (!gfFunctionsLoadedSuccessfully) {
         return;
@@ -288,7 +346,7 @@ void CommandBufferGLTestContext::presentCommandBuffer() {
 }
 
 bool CommandBufferGLTestContext::makeCurrent() {
-    return gfMakeCurrent(fDisplay, fSurface, fSurface, fContext) != EGL_FALSE;
+    return hookedMakeCurrent(fDisplay, fSurface, fSurface, fContext) != EGL_FALSE;
 }
 
 int CommandBufferGLTestContext::getStencilBits() {
diff --git a/tools/gpu/gl/command_buffer/GLTestContext_command_buffer.h b/tools/gpu/gl/command_buffer/GLTestContext_command_buffer.h
index 7582f16351..6a631be8fb 100644
--- a/tools/gpu/gl/command_buffer/GLTestContext_command_buffer.h
+++ b/tools/gpu/gl/command_buffer/GLTestContext_command_buffer.h
@@ -42,6 +42,8 @@ private:
 
     void onPlatformMakeCurrent() const override;
 
+    std::function<void()> onPlatformGetAutoContextRestore() const override;
+
     void onPlatformSwapBuffers() const override;
 
     GrGLFuncPtr onPlatformGetProcAddress(const char *name) const override;
diff --git a/tools/gpu/gl/debug/DebugGLTestContext.cpp b/tools/gpu/gl/debug/DebugGLTestContext.cpp
index f16692e8e0..e28a3a7f13 100644
--- a/tools/gpu/gl/debug/DebugGLTestContext.cpp
+++ b/tools/gpu/gl/debug/DebugGLTestContext.cpp
@@ -1203,6 +1203,7 @@ public:
 
 private:
     void onPlatformMakeCurrent() const override {}
+    std::function<void()> onPlatformGetAutoContextRestore() const override { return nullptr; }
     void onPlatformSwapBuffers() const override {}
     GrGLFuncPtr onPlatformGetProcAddress(const char*) const override { return nullptr; }
 };
diff --git a/tools/gpu/gl/egl/CreatePlatformGLTestContext_egl.cpp b/tools/gpu/gl/egl/CreatePlatformGLTestContext_egl.cpp
index 74cadfcb62..7fa88c094a 100644
--- a/tools/gpu/gl/egl/CreatePlatformGLTestContext_egl.cpp
+++ b/tools/gpu/gl/egl/CreatePlatformGLTestContext_egl.cpp
@@ -39,6 +39,16 @@ private:
     typedef sk_gpu_test::FenceSync INHERITED;
 };
 
+std::function<void()> context_restorer() {
+    auto display = eglGetCurrentDisplay();
+    auto dsurface = eglGetCurrentSurface(EGL_DRAW);
+    auto rsurface = eglGetCurrentSurface(EGL_READ);
+    auto context = eglGetCurrentContext();
+    return [display, dsurface, rsurface, context] {
+        eglMakeCurrent(display, dsurface, rsurface, context);
+    };
+}
+
 class EGLGLTestContext : public sk_gpu_test::GLTestContext {
 public:
     EGLGLTestContext(GrGLStandard forcedGpuAPI, EGLGLTestContext* shareContext);
@@ -53,6 +63,7 @@ private:
     void destroyGLContext();
 
     void onPlatformMakeCurrent() const override;
+    std::function<void()> onPlatformGetAutoContextRestore() const override;
     void onPlatformSwapBuffers() const override;
     GrGLFuncPtr onPlatformGetProcAddress(const char*) const override;
 
@@ -168,6 +179,7 @@ EGLGLTestContext::EGLGLTestContext(GrGLStandard forcedGpuAPI, EGLGLTestContext*
             continue;
         }
 
+        SkScopeExit restorer(context_restorer());
         if (!eglMakeCurrent(fDisplay, fSurface, fSurface, fContext)) {
             SkDebugf("eglMakeCurrent failed.  EGL Error: 0x%08x\n", eglGetError());
             this->destroyGLContext();
@@ -199,9 +211,11 @@ EGLGLTestContext::~EGLGLTestContext() {
 
 void EGLGLTestContext::destroyGLContext() {
     if (fDisplay) {
-        eglMakeCurrent(fDisplay, 0, 0, 0);
-
         if (fContext) {
+            if (eglGetCurrentContext() == fContext) {
+                // This will ensure that the context is immediately deleted.
+                eglMakeCurrent(fDisplay, EGL_NO_SURFACE, EGL_NO_SURFACE, EGL_NO_CONTEXT);
+            }
             eglDestroyContext(fDisplay, fContext);
             fContext = EGL_NO_CONTEXT;
         }
@@ -284,6 +298,13 @@ void EGLGLTestContext::onPlatformMakeCurrent() const {
     }
 }
 
+std::function<void()> EGLGLTestContext::onPlatformGetAutoContextRestore() const {
+    if (eglGetCurrentContext() == fContext) {
+        return nullptr;
+    }
+    return context_restorer();
+}
+
 void EGLGLTestContext::onPlatformSwapBuffers() const {
     if (!eglSwapBuffers(fDisplay, fSurface)) {
         SkDebugf("Could not complete eglSwapBuffers.\n");
diff --git a/tools/gpu/gl/glx/CreatePlatformGLTestContext_glx.cpp b/tools/gpu/gl/glx/CreatePlatformGLTestContext_glx.cpp
index 76b6d21661..cb1215261a 100644
--- a/tools/gpu/gl/glx/CreatePlatformGLTestContext_glx.cpp
+++ b/tools/gpu/gl/glx/CreatePlatformGLTestContext_glx.cpp
@@ -51,6 +51,13 @@ static int ctxErrorHandler(Display *dpy, XErrorEvent *ev) {
     return 0;
 }
 
+std::function<void()> context_restorer() {
+    auto display = glXGetCurrentDisplay();
+    auto drawable = glXGetCurrentDrawable();
+    auto context = glXGetCurrentContext();
+    return [display, drawable, context] { glXMakeCurrent(display, drawable, context); };
+}
+
 class GLXGLTestContext : public sk_gpu_test::GLTestContext {
 public:
     GLXGLTestContext(GrGLStandard forcedGpuAPI, GLXGLTestContext* shareList);
@@ -62,6 +69,7 @@ private:
                                         GLXContext glxSharedContext);
 
     void onPlatformMakeCurrent() const override;
+    std::function<void()> onPlatformGetAutoContextRestore() const override;
     void onPlatformSwapBuffers() const override;
     GrGLFuncPtr onPlatformGetProcAddress(const char*) const override;
 
@@ -214,6 +222,7 @@ GLXGLTestContext::GLXGLTestContext(GrGLStandard forcedGpuAPI, GLXGLTestContext*
         //SkDebugf("Direct GLX rendering context obtained.\n");
     }
 
+    SkScopeExit restorer(context_restorer());
     //SkDebugf("Making context current.\n");
     if (!glXMakeCurrent(fDisplay, fGlxPixmap, fContext)) {
       SkDebugf("Could not set the context.\n");
@@ -245,9 +254,11 @@ GLXGLTestContext::~GLXGLTestContext() {
 
 void GLXGLTestContext::destroyGLContext() {
     if (fDisplay) {
-        glXMakeCurrent(fDisplay, 0, 0);
-
         if (fContext) {
+            if (glXGetCurrentContext() == fContext) {
+                // This will ensure that the context is immediately deleted.
+                glXMakeContextCurrent(fDisplay, None, None, nullptr);
+            }
             glXDestroyContext(fDisplay, fContext);
             fContext = nullptr;
         }
@@ -334,6 +345,13 @@ void GLXGLTestContext::onPlatformMakeCurrent() const {
     }
 }
 
+std::function<void()> GLXGLTestContext::onPlatformGetAutoContextRestore() const {
+    if (glXGetCurrentContext() == fContext) {
+        return nullptr;
+    }
+    return context_restorer();
+}
+
 void GLXGLTestContext::onPlatformSwapBuffers() const {
     glXSwapBuffers(fDisplay, fGlxPixmap);
 }
diff --git a/tools/gpu/gl/iOS/CreatePlatformGLTestContext_iOS.mm b/tools/gpu/gl/iOS/CreatePlatformGLTestContext_iOS.mm
index e897e8c7c4..65d2861483 100644
--- a/tools/gpu/gl/iOS/CreatePlatformGLTestContext_iOS.mm
+++ b/tools/gpu/gl/iOS/CreatePlatformGLTestContext_iOS.mm
@@ -14,6 +14,11 @@
 
 namespace {
 
+std::function<void()> context_restorer() {
+    EAGLContext* context = [EAGLContext currentContext];
+    return [context] { [EAGLContext setCurrentContext:context]; };
+}
+
 class IOSGLTestContext : public sk_gpu_test::GLTestContext {
 public:
     IOSGLTestContext(IOSGLTestContext* shareContext);
@@ -23,6 +28,7 @@ private:
     void destroyGLContext();
 
     void onPlatformMakeCurrent() const override;
+    std::function<void()> onPlatformGetAutoContextRestore() const override;
     void onPlatformSwapBuffers() const override;
     GrGLFuncPtr onPlatformGetProcAddress(const char*) const override;
 
@@ -41,6 +47,7 @@ IOSGLTestContext::IOSGLTestContext(IOSGLTestContext* shareContext)
     } else {
         fEAGLContext = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES2];
     }
+    SkScopeExit restorer(context_restorer());
     [EAGLContext setCurrentContext:fEAGLContext];
 
     sk_sp<const GrGLInterface> gl(GrGLCreateNativeInterface());
@@ -70,6 +77,7 @@ IOSGLTestContext::~IOSGLTestContext() {
 void IOSGLTestContext::destroyGLContext() {
     if (fEAGLContext) {
         if ([EAGLContext currentContext] == fEAGLContext) {
+            // This will ensure that the context is immediately deleted.
             [EAGLContext setCurrentContext:nil];
         }
         fEAGLContext = nil;
@@ -86,6 +94,13 @@ void IOSGLTestContext::onPlatformMakeCurrent() const {
     }
 }
 
+std::function<void()> IOSGLTestContext::onPlatformGetAutoContextRestore() const {
+    if ([EAGLContext currentContext] == fEAGLContext) {
+		return nullptr;
+	}
+    return context_restorer();
+}
+
 void IOSGLTestContext::onPlatformSwapBuffers() const { }
 
 GrGLFuncPtr IOSGLTestContext::onPlatformGetProcAddress(const char* procName) const {
diff --git a/tools/gpu/gl/mac/CreatePlatformGLTestContext_mac.cpp b/tools/gpu/gl/mac/CreatePlatformGLTestContext_mac.cpp
index a94f503d48..9f1c61e564 100644
--- a/tools/gpu/gl/mac/CreatePlatformGLTestContext_mac.cpp
+++ b/tools/gpu/gl/mac/CreatePlatformGLTestContext_mac.cpp
@@ -14,6 +14,12 @@
 #include <dlfcn.h>
 
 namespace {
+
+std::function<void()> context_restorer() {
+    auto context = CGLGetCurrentContext();
+    return [context] { CGLSetCurrentContext(context); };
+}
+
 class MacGLTestContext : public sk_gpu_test::GLTestContext {
 public:
     MacGLTestContext(MacGLTestContext* shareContext);
@@ -23,6 +29,7 @@ private:
     void destroyGLContext();
 
     void onPlatformMakeCurrent() const override;
+    std::function<void()> onPlatformGetAutoContextRestore() const override;
     void onPlatformSwapBuffers() const override;
     GrGLFuncPtr onPlatformGetProcAddress(const char*) const override;
 
@@ -58,6 +65,7 @@ MacGLTestContext::MacGLTestContext(MacGLTestContext* shareContext)
         return;
     }
 
+    SkScopeExit restorer(context_restorer());
     CGLSetCurrentContext(fContext);
 
     sk_sp<const GrGLInterface> gl(GrGLCreateNativeInterface());
@@ -86,6 +94,10 @@ MacGLTestContext::~MacGLTestContext() {
 
 void MacGLTestContext::destroyGLContext() {
     if (fContext) {
+        if (CGLGetCurrentContext() == fContext) {
+            // This will ensure that the context is immediately deleted.
+            CGLSetCurrentContext(nullptr);
+        }
         CGLReleaseContext(fContext);
         fContext = nullptr;
     }
@@ -98,6 +110,13 @@ void MacGLTestContext::onPlatformMakeCurrent() const {
     CGLSetCurrentContext(fContext);
 }
 
+std::function<void()> MacGLTestContext::onPlatformGetAutoContextRestore() const {
+    if (CGLGetCurrentContext() == fContext) {
+        return nullptr;
+    }
+    return context_restorer();
+}
+
 void MacGLTestContext::onPlatformSwapBuffers() const {
     CGLFlushDrawable(fContext);
 }
diff --git a/tools/gpu/gl/null/NullGLTestContext.cpp b/tools/gpu/gl/null/NullGLTestContext.cpp
index 894de0709a..9e7279b501 100644
--- a/tools/gpu/gl/null/NullGLTestContext.cpp
+++ b/tools/gpu/gl/null/NullGLTestContext.cpp
@@ -22,6 +22,7 @@ public:
 
 private:
     void onPlatformMakeCurrent() const override {}
+    std::function<void()> onPlatformGetAutoContextRestore() const override { return nullptr; }
     void onPlatformSwapBuffers() const override {}
     GrGLFuncPtr onPlatformGetProcAddress(const char*) const override { return nullptr; }
 };
diff --git a/tools/gpu/gl/win/CreatePlatformGLTestContext_win.cpp b/tools/gpu/gl/win/CreatePlatformGLTestContext_win.cpp
index 0e97153794..5fc355a22a 100644
--- a/tools/gpu/gl/win/CreatePlatformGLTestContext_win.cpp
+++ b/tools/gpu/gl/win/CreatePlatformGLTestContext_win.cpp
@@ -16,6 +16,12 @@
 
 namespace {
 
+std::function<void()> context_restorer() {
+    auto glrc = wglGetCurrentContext();
+    auto dc = wglGetCurrentDC();
+    return [glrc, dc] { wglMakeCurrent(dc, glrc); };
+}
+
 class WinGLTestContext : public sk_gpu_test::GLTestContext {
 public:
     WinGLTestContext(GrGLStandard forcedGpuAPI, WinGLTestContext* shareContext);
@@ -25,6 +31,7 @@ private:
     void destroyGLContext();
 
     void onPlatformMakeCurrent() const override;
+    std::function<void()> onPlatformGetAutoContextRestore() const override;
     void onPlatformSwapBuffers() const override;
     GrGLFuncPtr onPlatformGetProcAddress(const char* name) const override;
 
@@ -113,6 +120,7 @@ WinGLTestContext::WinGLTestContext(GrGLStandard forcedGpuAPI, WinGLTestContext*
         glrc = fPbufferContext->getGLRC();
     }
 
+    SkScopeExit restorer(context_restorer());
     if (!(wglMakeCurrent(dc, glrc))) {
         SkDebugf("Could not set the context.\n");
         this->destroyGLContext();
@@ -142,6 +150,7 @@ WinGLTestContext::~WinGLTestContext() {
 void WinGLTestContext::destroyGLContext() {
     SkSafeSetNull(fPbufferContext);
     if (fGlRenderContext) {
+        // This deletes the context immediately even if it is current.
         wglDeleteContext(fGlRenderContext);
         fGlRenderContext = 0;
     }
@@ -172,6 +181,13 @@ void WinGLTestContext::onPlatformMakeCurrent() const {
     }
 }
 
+std::function<void()> WinGLTestContext::onPlatformGetAutoContextRestore() const {
+    if (wglGetCurrentContext() == fGlRenderContext) {
+        return nullptr;
+    }
+    return context_restorer();
+}
+
 void WinGLTestContext::onPlatformSwapBuffers() const {
     HDC dc;