mix-blend-mode implementation for accelerated 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 b0c5399d32e3a3fd06c1963eb585e671e52a6ca4..6b61f4e0780b8845a06f83dbd289318a6ff03f8f 100644
--- a/cc/layers/layer_impl.cc
+++ b/cc/layers/layer_impl.cc
@@ -50,6 +50,8 @@ LayerImpl::LayerImpl(LayerTreeImpl* tree_impl, int id)
       masks_to_bounds_(false),
       contents_opaque_(false),
       opacity_(1.0),
+      blend_mode_(SkXfermode::kSrcOver_Mode),
+      is_root_for_isolated_group_(false),
       preserves_3d_(false),
       use_parent_backface_visibility_(false),
       draw_checkerboard_for_missing_tiles_(false),
@@ -509,6 +511,8 @@ void LayerImpl::PushPropertiesTo(LayerImpl* layer) {
   layer->SetTouchEventHandlerRegion(touch_event_handler_region_);
   layer->SetContentsOpaque(contents_opaque_);
   layer->SetOpacity(opacity_);
+  layer->SetBlendMode(blend_mode_);
+  layer->SetIsRootForIsolatedGroup(is_root_for_isolated_group_);
   layer->SetPosition(position_);
   layer->SetIsContainerForFixedPositionLayers(
       is_container_for_fixed_position_layers_);
@@ -875,6 +879,22 @@ bool LayerImpl::OpacityIsAnimatingOnImplOnly() const {
   return opacity_animation && opacity_animation->is_impl_only();
 }
 
+void LayerImpl::SetBlendMode(SkXfermode::Mode blendMode) {
+  if (blend_mode_ == blendMode)
+    return;
+
+  blend_mode_ = blendMode;
+  NoteLayerSurfacePropertyChanged();
+}
+
+void LayerImpl::SetIsRootForIsolatedGroup(bool root) {
+  if (is_root_for_isolated_group_ == root)
+    return;
+
+  is_root_for_isolated_group_ = root;
+  NoteLayerSurfacePropertyChanged();
+}
+
 void LayerImpl::SetPosition(gfx::PointF position) {
   if (position_ == position)
     return;
@@ -1266,6 +1286,9 @@ CompositingReasonsAsValue(CompositingReasons reasons) {
   if (reasons & kCompositingReasonOutOfFlowClipping)
     reason_list->AppendString("Has clipping ancestor");
 
+  if (reasons & kCompositingReasonIsolateCompositedDescendants)
+    reason_list->AppendString("Should isolate composited dscendants");
+
   return reason_list.PassAs<base::Value>();
 }