Add CompositingReasons to compositor layers.

cc/layers/layer_impl.cc

Index: cc/layers/layer_impl.cc
diff --git a/cc/layers/layer_impl.cc b/cc/layers/layer_impl.cc
index b6a4120eb63c39bc0dd770137d9e6c3004d5d507..63415469035f4faa2788054b1594e7e381298439 100644
--- a/cc/layers/layer_impl.cc
+++ b/cc/layers/layer_impl.cc
@@ -54,6 +54,7 @@ LayerImpl::LayerImpl(LayerTreeImpl* tree_impl, int id)
       force_render_surface_(false),
       is_container_for_fixed_position_layers_(false),
       draw_depth_(0.f),
+      compositing_reasons_(kCompositingReasonUnknown),
 #ifndef NDEBUG
       between_will_draw_and_did_draw_(false),
 #endif
@@ -352,6 +353,7 @@ void LayerImpl::PushPropertiesTo(LayerImpl* layer) {
   layer->SetContentBounds(content_bounds());
   layer->SetContentsScale(contents_scale_x(), contents_scale_y());
   layer->SetDebugName(debug_name_);
+  layer->SetCompositingReasons(compositing_reasons_);
   layer->SetDoubleSided(double_sided_);
   layer->SetDrawCheckerboardForMissingTiles(
       draw_checkerboard_for_missing_tiles_);
@@ -1001,12 +1003,134 @@ void LayerImpl::SetVerticalScrollbarLayer(ScrollbarLayerImpl* scrollbar_layer) {
     vertical_scrollbar_layer_->set_scroll_layer_id(id());
 }
 
+static scoped_ptr<base::Value>
+CompositingReasonsAsValue(CompositingReasons reasons) {
+  scoped_ptr<base::ListValue> reason_list(new base::ListValue());
+
+  if (reasons == kCompositingReasonUnknown) {
+    reason_list->AppendString("No reasons given");
+    return reason_list.PassAs<base::Value>();
+  }
+
+  if (reasons & kCompositingReason3DTransform)
+    reason_list->AppendString("Has a 3d Transform");
+
+  if (reasons & kCompositingReasonVideo)
+    reason_list->AppendString("Is accelerated video");
+
+  if (reasons & kCompositingReasonCanvas)
+    reason_list->AppendString("Is accelerated canvas");
+
+  if (reasons & kCompositingReasonPlugin)
+    reason_list->AppendString("Is accelerated plugin");
+
+  if (reasons & kCompositingReasonIFrame)
+    reason_list->AppendString("Is accelerated iframe");
+
+  if (reasons & kCompositingReasonBackfaceVisibilityHidden)
+    reason_list->AppendString("Has backface-visibility: hidden");
+
+  if (reasons & kCompositingReasonAnimation)
+    reason_list->AppendString("Has accelerated animation or transition");
+
+  if (reasons & kCompositingReasonFilters)
+    reason_list->AppendString("Has accelerated filters");
+
+  if (reasons & kCompositingReasonPositionFixed)
+    reason_list->AppendString("Is fixed position");
+
+  if (reasons & kCompositingReasonPositionSticky)
+    reason_list->AppendString("Is sticky position");
+
+  if (reasons & kCompositingReasonOverflowScrollingTouch)
+    reason_list->AppendString("Is a scrollable overflow element");
+
+  if (reasons & kCompositingReasonBlending)
+    reason_list->AppendString("Has a blend mode");
+
+  if (reasons & kCompositingReasonAssumedOverlap)
+    reason_list->AppendString("Might overlap a composited animation");
+
+  if (reasons & kCompositingReasonOverlap)
+    reason_list->AppendString("Overlaps other composited content");
+
+  if (reasons & kCompositingReasonNegativeZIndexChildren) {
+    reason_list->AppendString("Might overlap negative z-index "
+                              "composited content");
+  }
+
+  if (reasons & kCompositingReasonTransformWithCompositedDescendants) {
+    reason_list->AppendString("Has transform needed by a "
+                              "composited descendant");
+  }
+
+  if (reasons & kCompositingReasonOpacityWithCompositedDescendants)
+    reason_list->AppendString("Has opacity needed by a composited descendant");
+
+  if (reasons & kCompositingReasonMaskWithCompositedDescendants)
+    reason_list->AppendString("Has a mask needed by a composited descendant");
+
+  if (reasons & kCompositingReasonReflectionWithCompositedDescendants)
+    reason_list->AppendString("Has a reflection with a composited descendant");
+
+  if (reasons & kCompositingReasonFilterWithCompositedDescendants)
+    reason_list->AppendString("Has filter effect with a composited descendant");
+
+  if (reasons & kCompositingReasonBlendingWithCompositedDescendants)
+    reason_list->AppendString("Has a blend mode with a composited descendant");
+
+  if (reasons & kCompositingReasonClipsCompositingDescendants)
+    reason_list->AppendString("Clips a composited descendant");
+
+  if (reasons & kCompositingReasonPerspective) {
+    reason_list->AppendString("Has a perspective transform needed by a "
+                              "composited 3d descendant");
+  }
+
+  if (reasons & kCompositingReasonPreserve3D) {
+    reason_list->AppendString("Has preserves-3d style with composited "
+                              "3d descendant");
+  }
+
+  if (reasons & kCompositingReasonReflectionOfCompositedParent)
+    reason_list->AppendString("Is the reflection of a composited layer");
+
+  if (reasons & kCompositingReasonRoot)
+    reason_list->AppendString("Is the root");
+
+  if (reasons & kCompositingReasonLayerForClip)
+    reason_list->AppendString("Convenience layer, to clip subtree");
+
+  if (reasons & kCompositingReasonLayerForScrollbar)
+    reason_list->AppendString("Convenience layer for rendering scrollbar");
+
+  if (reasons & kCompositingReasonLayerForScrollingContainer)
+    reason_list->AppendString("Convenience layer, the scrolling container");
+
+  if (reasons & kCompositingReasonLayerForForeground) {
+    reason_list->AppendString("Convenience layer, foreground when main layer "
+                              "has negative z-index composited content");
+  }
+
+  if (reasons & kCompositingReasonLayerForBackground) {
+    reason_list->AppendString("Convenience layer, background when main layer "
+                              "has a composited background");
+  }
+
+  if (reasons & kCompositingReasonLayerForMask)
+    reason_list->AppendString("Is a mask layer");
+
+  return reason_list.PassAs<base::Value>();
+}
+
 void LayerImpl::AsValueInto(base::DictionaryValue* state) const {
   TracedValue::MakeDictIntoImplicitSnapshot(state, LayerTypeAsString(), this);
   state->SetInteger("layer_id", id());
   state->Set("bounds", MathUtil::AsValue(bounds()).release());
   state->SetInteger("draws_content", DrawsContent());
   state->SetInteger("gpu_memory_usage", GPUMemoryUsageInBytes());
+  state->Set("compositing_reasons",
+             CompositingReasonsAsValue(compositing_reasons_).release());
 
   bool clipped;
   gfx::QuadF layer_quad = MathUtil::MapQuad(