Add support for GL_EXT_raster_multisample

Updates the GrGLGpu to call glRasterSamplesEXT when multisample is
enabled for a mixed sampled render target, but the stencil test is not
active.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1666563003

Review URL: https://codereview.chromium.org/1666563003

1 files changed, 4 insertions, 0 deletions

diff --git a/include/gpu/GrCaps.h b/include/gpu/GrCaps.h
index 05da8d7cad..944fb1481c 100644
--- a/include/gpu/GrCaps.h
+++ b/include/gpu/GrCaps.h
@@ -211,6 +211,9 @@ public:
     int maxColorSampleCount() const { return fMaxColorSampleCount; }
     // Will be 0 if MSAA is not supported
     int maxStencilSampleCount() const { return fMaxStencilSampleCount; }
+    // Will be 0 if raster multisample is not supported. Raster multisample is a special HW mode
+    // where the rasterizer runs with more samples than are in the target framebuffer.
+    int maxRasterSamples() const { return fMaxRasterSamples; }
     // We require the sample count to be less than maxColorSampleCount and maxStencilSampleCount.
     // If we are using mixed samples, we only care about stencil.
     int maxSampleCount() const {
@@ -291,6 +294,7 @@ protected:
     int fMaxTileSize;
     int fMaxColorSampleCount;
     int fMaxStencilSampleCount;
+    int fMaxRasterSamples;
 
 private:
     virtual void onApplyOptionsOverrides(const GrContextOptions&) {};