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 e58ed0b73b7c33c01b62ae654d8ec3bdf1664704..392b185d94842e1ce149d91e71d4699f54905d0d 100644
--- a/cc/resources/resource_provider.cc
+++ b/cc/resources/resource_provider.cc
@@ -12,6 +12,7 @@
 #include "base/stl_util.h"
 #include "base/strings/string_split.h"
 #include "base/strings/string_util.h"
+#include "cc/base/switches.h"
 #include "cc/base/util.h"
 #include "cc/output/gl_renderer.h"  // For the GLC() macro.
 #include "cc/resources/platform_color.h"
@@ -412,10 +413,18 @@ 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()) {
+      // 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() {
@@ -432,6 +441,7 @@ 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();

[nduca, 2014/03/01 22:02:28]

i think it woudl be better if you obtained this from ganesh. that is, skia
should decide msaa mode, then we should just grcontext for the preferred raster
sample count. Eg gr_context->getRasterSampleCount(). Then skia can take the
burden/logistics on of testing for different msaa modes if thats what they are
wanting to support for some GL renderer string for instance. and from the
compositors point of view, we're not involved.

         skia::RefPtr<GrTexture> gr_texture =
             skia::AdoptRef(gr_context->wrapBackendTexture(desc));
         surface = skia::AdoptRef(
@@ -1217,6 +1227,7 @@ ResourceProvider::ResourceProvider(OutputSurface* output_surface,
       use_compressed_texture_etc1_(false),
       max_texture_size_(0),
       best_texture_format_(RGBA_8888),
+      num_gpu_rasterization_samples_(0),
       use_rgba_4444_texture_format_(use_rgba_4444_texture_format),
       id_allocation_chunk_size_(id_allocation_chunk_size) {
   DCHECK(output_surface_->HasClient());
@@ -1260,6 +1271,20 @@ bool ResourceProvider::InitializeGL() {
   GLC(gl, gl->GetIntegerv(GL_MAX_TEXTURE_SIZE, &max_texture_size_));
   best_texture_format_ = PlatformColor::BestTextureFormat(use_bgra);
 
+  switch (switches::GetGpuRasterizationType()) {
+    default:
+      NOTREACHED();
+    case switches::GpuRasterizationGpu:
+      num_gpu_rasterization_samples_ = 0;
+      break;
+    case switches::GpuRasterizationMsaa4:
+      num_gpu_rasterization_samples_ = 4;
+      break;
+    case switches::GpuRasterizationMsaa16:
+      num_gpu_rasterization_samples_ = 16;
+      break;
+  }
+
   texture_id_allocator_.reset(
       new TextureIdAllocator(gl, id_allocation_chunk_size_));
   buffer_id_allocator_.reset(