cc: Trace event for veto reason

Allow a pointer to a |reason| string to be passed through the
|Picture| to the |SkPicture|.

Create an instant event when the gpu rasterization veto
is hit.

BUG=434613

Review URL: https://codereview.chromium.org/780683002

Cr-Commit-Position: refs/heads/master@{#306683}

3 files changed, 16 insertions, 12 deletions

diff --git a/cc/resources/picture.cc b/cc/resources/picture.cc
index 5b90571..6530866 100644
--- a/cc/resources/picture.cc
+++ b/cc/resources/picture.cc
@@ -175,17 +175,13 @@ 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 {
diff --git a/cc/resources/picture.h b/cc/resources/picture.h
index 771d715..ec2ff4b 100644
--- a/cc/resources/picture.h
+++ b/cc/resources/picture.h
@@ -65,7 +65,7 @@ class CC_EXPORT Picture
   // Has Record() been called yet?
   bool HasRecording() const { return picture_.get() != NULL; }
 
-  bool IsSuitableForGpuRasterization() const;
+  bool IsSuitableForGpuRasterization(const char** reason) const;
   int ApproximateOpCount() const;
   size_t ApproximateMemoryUsage() const;
 
diff --git a/cc/resources/picture_pile.cc b/cc/resources/picture_pile.cc
index d94ce7c..c3050c3 100644
--- a/cc/resources/picture_pile.cc
+++ b/cc/resources/picture_pile.cc
@@ -556,8 +556,16 @@ void PicturePile::CreatePictures(ContentLayerClient* painter,
       // even if that content is replaced by gpu-friendly content.
       // This is an optimization to avoid iterating though all pictures in
       // the pile after each invalidation.
-      is_suitable_for_gpu_rasterization_ &=
-          picture->IsSuitableForGpuRasterization();
+      if (is_suitable_for_gpu_rasterization_) {
+        const char* reason = nullptr;
+        is_suitable_for_gpu_rasterization_ &=
+            picture->IsSuitableForGpuRasterization(&reason);
+
+        if (!is_suitable_for_gpu_rasterization_) {
+          TRACE_EVENT_INSTANT1("cc", "GPU Rasterization Veto",
+                               TRACE_EVENT_SCOPE_THREAD, "reason", reason);
+        }
+      }
     }
 
     bool found_tile_for_recorded_picture = false;