Use MSAA in GPU rasterization if Skia suggests it

cc/resources/resource_provider.cc

Index: cc/resources/resource_provider.cc
diff --git a/cc/resources/resource_provider.cc b/cc/resources/resource_provider.cc
index 7ad1492aedbb12c6944005ba4533cb5a34a9fbd4..87b1c7a1fbf2eb9bfa7fc32927df8ca73bece18a 100644
--- a/cc/resources/resource_provider.cc
+++ b/cc/resources/resource_provider.cc
@@ -61,6 +61,9 @@ namespace {
 const double kSoftwareUploadTickRate = 0.000250;
 const double kTextureUploadTickRate = 0.004;
 
+// Display density in dots per inch at scale factor 1.0.

[nduca, 2014/04/23 23:07:24]

what the heck is this? why do you need this?

+const float kDisplayDensityScaleFactor = 160.0f;
+
 GLenum TextureToStorageFormat(ResourceFormat format) {
   GLenum storage_format = GL_RGBA8_OES;
   switch (format) {
@@ -444,10 +447,18 @@ SkCanvas* ResourceProvider::DirectRasterBuffer::DoLockForWrite() {
 }
 
 bool ResourceProvider::DirectRasterBuffer::DoUnlockForWrite() {
-  // generationID returns a non-zero, unique value corresponding to the content
-  // of surface. Hence, a change since DoLockForWrite was called means the
-  // surface has changed.
-  return surface_ ? surface_generation_id_ != surface_->generationID() : false;
+  if (surface_) {
+    // generationID returns a non-zero, unique value corresponding to the
+    // content of surface. Hence, a change since DoLockForWrite was called
+    // means the surface has changed.
+    if (surface_generation_id_ != surface_->generationID()) {

[nduca, 2014/04/23 23:07:24]

can you do this as a separate change please?

+      // Flush any pending or deferred work canvas or device might have. This
+      // also resolves the potential MSAA.
+      surface_->getCanvas()->flush();
+      return true;
+    }
+  }
+  return false;
 }
 
 skia::RefPtr<SkSurface> ResourceProvider::DirectRasterBuffer::CreateSurface() {
@@ -464,6 +475,8 @@ skia::RefPtr<SkSurface> ResourceProvider::DirectRasterBuffer::CreateSurface() {
         desc.fConfig = ToGrPixelConfig(resource()->format);
         desc.fOrigin = kTopLeft_GrSurfaceOrigin;
         desc.fTextureHandle = resource()->gl_id;
+        desc.fSampleCnt = resource_provider()->num_gpu_rasterization_samples(
+            resource()->format);
         skia::RefPtr<GrTexture> gr_texture =
             skia::AdoptRef(gr_context->wrapBackendTexture(desc));
         surface = skia::AdoptRef(
@@ -624,6 +637,13 @@ ResourceProvider::~ResourceProvider() {
   CleanUpGLIfNeeded();
 }
 
+unsigned ResourceProvider::num_gpu_rasterization_samples(
+    ResourceFormat format) const {
+  const float dpi =
+      kDisplayDensityScaleFactor * output_surface_->SurfaceScaleFactor();
+  return GrContext()->getRecommendedSampleCount(ToGrPixelConfig(format), dpi);
+}
+
 bool ResourceProvider::InUseByConsumer(ResourceId id) {
   Resource* resource = GetResource(id);
   return resource->lock_for_read_count > 0 || resource->exported_count > 0 ||