cc: Trace event for veto reason

cc/resources/picture.cc

Index: cc/resources/picture.cc
diff --git a/cc/resources/picture.cc b/cc/resources/picture.cc
index 9a45ad19a67b666a4ce8923aa7bdf41a71546fff..830541b7e3028e37a9ed0f6587f0ad38aef75a18 100644
--- a/cc/resources/picture.cc
+++ b/cc/resources/picture.cc
@@ -174,17 +174,13 @@ Picture::~Picture() {
     TRACE_DISABLED_BY_DEFAULT("cc.debug"), "cc::Picture", this);
 }
 
-bool Picture::IsSuitableForGpuRasterization() const {
+bool Picture::IsSuitableForGpuRasterization(const char** reason) const {
   DCHECK(picture_);
 
-  // TODO(alokp): SkPicture::suitableForGpuRasterization needs a GrContext.
-  // Ideally this GrContext should be the same as that for rasterizing this
-  // picture. But we are on the main thread while the rasterization context
-  // may be on the compositor or raster thread.
-  // SkPicture::suitableForGpuRasterization is not implemented yet.
-  // Pass a NULL context for now and discuss with skia folks if the context
-  // is really needed.
-  return picture_->suitableForGpuRasterization(NULL);
+  // TODO(hendrikw): SkPicture::suitableForGpuRasterization takes a GrContext.
+  // Currently the GrContext isn't used, and should probably be removed from
+  // skia.
+  return picture_->suitableForGpuRasterization(nullptr, reason);
 }
 
 int Picture::ApproximateOpCount() const {