Add config options to run different GPU APIs to dm and nanobench

Add extended config specification form that can be used to run different
gpu backend with different APIs.

The configs can be specified with the form:
gpu(api=string,dit=bool,nvpr=bool,samples=int)

This replaces and removes the --gpuAPI flag.

All existing configs should still work.

Adds following documentation:

out/Debug/dm --help config

Flags:
    --config:	type: string	default: 565 8888 gpu nonrendering
        Options: 565 8888 debug gpu gpudebug gpudft gpunull msaa16 msaa4
        nonrendering null nullgpu nvprmsaa16 nvprmsaa4 pdf pdf_poppler skp svg
        xps or use extended form 'backend(option=value,...)'.

        Extended form: 'backend(option=value,...)'

        Possible backends and options:

        gpu(api=string,dit=bool,nvpr=bool,samples=int)	GPU backend
        	api	type: string	default: native.
        	    Select graphics API to use with gpu backend.
        	    Options:
        		native			Use platform default OpenGL or OpenGL ES backend.
        		gl    			Use OpenGL.
        		gles  			Use OpenGL ES.
        		debug 			Use debug OpenGL.
        		null  			Use null OpenGL.
        	dit	type: bool	default: false.
        	    Use device independent text.
        	nvpr	type: bool	default: false.
        	    Use NV_path_rendering OpenGL and OpenGL ES extension.
        	samples	type: int	default: 0.
        	    Use multisampling with N samples.

        Predefined configs:

        	gpu      	= gpu()
        	msaa4    	= gpu(samples=4)
        	msaa16   	= gpu(samples=16)
        	nvprmsaa4	= gpu(nvpr=true,samples=4)
        	nvprmsaa16	= gpu(nvpr=true,samples=16)
        	gpudft    	= gpu(dit=true)
        	gpudebug  	= gpu(api=debug)
        	gpunull   	= gpu(api=null)
        	debug     	= gpu(api=debug)
        	nullgpu   	= gpu(api=null)

BUG=skia:2992

Committed: https://skia.googlesource.com/skia/+/e13ca329fca4c28cf4e078561f591ab27b743d23
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1490113005

Committed: https://skia.googlesource.com/skia/+/c8b4336444e7b90382e04e33665fb3b8490b825b

Committed: https://skia.googlesource.com/skia/+/9ebc3f0ee6db215dde461dc4777d85988cf272dd

Review URL: https://codereview.chromium.org/1490113005

4 files changed, 9 insertions, 13 deletions

diff --git a/src/gpu/gl/SkNullGLContext.cpp b/src/gpu/gl/SkNullGLContext.cpp
index e7270c32c4..dafa1ef0bc 100644
--- a/src/gpu/gl/SkNullGLContext.cpp
+++ b/src/gpu/gl/SkNullGLContext.cpp
@@ -578,10 +578,7 @@ static void set_current_context_from_interface(const GrGLInterface* interface) {
 }
 #endif
 
-SkNullGLContext* SkNullGLContext::Create(GrGLStandard forcedGpuAPI) {
-    if (kGLES_GrGLStandard == forcedGpuAPI) {
-        return nullptr;
-    }
+SkNullGLContext* SkNullGLContext::Create() {
     SkNullGLContext* ctx = new SkNullGLContext;
     if (!ctx->isValid()) {
         delete ctx;
diff --git a/src/gpu/gl/angle/SkANGLEGLContext.cpp b/src/gpu/gl/angle/SkANGLEGLContext.cpp
index 54ef02d492..2c9f38e1d9 100644
--- a/src/gpu/gl/angle/SkANGLEGLContext.cpp
+++ b/src/gpu/gl/angle/SkANGLEGLContext.cpp
@@ -180,7 +180,12 @@ GrGLuint SkANGLEGLContext::eglImageToExternalTexture(GrEGLImage image) const {
 }
 
 SkGLContext* SkANGLEGLContext::createNew() const {
-    SkGLContext* ctx = SkANGLEGLContext::Create(this->gl()->fStandard, fIsGLBackend);
+#ifdef SK_BUILD_FOR_WIN
+    SkGLContext* ctx = fIsGLBackend ? SkANGLEGLContext::CreateOpenGL()
+                                    : SkANGLEGLContext::CreateDirectX();
+#else
+    SkGLContext* ctx = SkANGLEGLContext::CreateOpenGL();
+#endif
     if (ctx) {
         ctx->makeCurrent();
     }
diff --git a/src/gpu/gl/debug/SkDebugGLContext.h b/src/gpu/gl/debug/SkDebugGLContext.h
index abbcf559c5..113a254e0b 100644
--- a/src/gpu/gl/debug/SkDebugGLContext.h
+++ b/src/gpu/gl/debug/SkDebugGLContext.h
@@ -14,10 +14,7 @@ class SkDebugGLContext : public SkGLContext {
 public:
     ~SkDebugGLContext() override;
 
-    static SkDebugGLContext* Create(GrGLStandard forcedGpuAPI) {
-        if (kGLES_GrGLStandard == forcedGpuAPI) {
-            return nullptr;
-        }
+    static SkDebugGLContext* Create() {
         return new SkDebugGLContext;
     }
 private:
diff --git a/src/gpu/gl/mesa/SkMesaGLContext.h b/src/gpu/gl/mesa/SkMesaGLContext.h
index a58f1c890e..a9c77a81da 100644
--- a/src/gpu/gl/mesa/SkMesaGLContext.h
+++ b/src/gpu/gl/mesa/SkMesaGLContext.h
@@ -19,10 +19,7 @@ private:
 public:
     ~SkMesaGLContext() override;
 
-    static SkMesaGLContext* Create(GrGLStandard forcedGpuAPI) {
-        if (kGLES_GrGLStandard == forcedGpuAPI) {
-            return nullptr;
-        }
+    static SkMesaGLContext* Create() {
         SkMesaGLContext* ctx = new SkMesaGLContext;
         if (!ctx->isValid()) {
             delete ctx;