mix-blend-mode implementation for accelerated layers

cc/layers/layer.cc

Index: cc/layers/layer.cc
diff --git a/cc/layers/layer.cc b/cc/layers/layer.cc
index b10112afd144ff73c2d6f3d69809053b17af46eb..da2e3ee84efa8ec095535f526d120e28b2445938 100644
--- a/cc/layers/layer.cc
+++ b/cc/layers/layer.cc
@@ -47,6 +47,8 @@ Layer::Layer()
       background_color_(0),
       compositing_reasons_(kCompositingReasonUnknown),
       opacity_(1.f),
+      blend_mode_(SkXfermode::kSrcOver_Mode),
+      is_root_for_isolated_group_(false),
       anchor_point_z_(0.f),
       is_container_for_fixed_position_layers_(false),
       is_drawable_(false),
@@ -125,7 +127,8 @@ void Layer::SetLayerTreeHost(LayerTreeHost* host) {
 
   if (host && layer_animation_controller_->has_any_animation())
     host->SetNeedsCommit();
-  if (host && (!filters_.IsEmpty() || !background_filters_.IsEmpty()))
+  if (host && (!filters_.IsEmpty() || !background_filters_.IsEmpty() ||
+               !uses_default_blend_mode()))
     layer_tree_host_->set_needs_filter_context();
 }
 
@@ -505,6 +508,22 @@ bool Layer::OpacityCanAnimateOnImplThread() const {
   return false;
 }
 
+void Layer::SetBlendMode(SkXfermode::Mode blend_mode) {
+  if (blend_mode_ == blend_mode)
+    return;
+  blend_mode_ = blend_mode;
+  SetNeedsCommit();
+  if (!uses_default_blend_mode() && layer_tree_host_)
+    layer_tree_host_->set_needs_filter_context();
+}
+
+void Layer::SetIsRootForIsolatedGroup(bool root) {
+  if (is_root_for_isolated_group_ == root)
+    return;
+  is_root_for_isolated_group_ = root;
+  SetNeedsCommit();
+}
+
 void Layer::SetContentsOpaque(bool opaque) {
   DCHECK(IsPropertyChangeAllowed());
   if (contents_opaque_ == opaque)
@@ -832,6 +851,8 @@ void Layer::PushPropertiesTo(LayerImpl* layer) {
   if (!layer->OpacityIsAnimatingOnImplOnly() && !OpacityIsAnimating())
     layer->SetOpacity(opacity_);
   DCHECK(!(OpacityIsAnimating() && layer->OpacityIsAnimatingOnImplOnly()));
+  layer->SetBlendMode(blend_mode_);
+  layer->SetIsRootForIsolatedGroup(is_root_for_isolated_group_);
   layer->SetPosition(position_);
   layer->SetIsContainerForFixedPositionLayers(
       IsContainerForFixedPositionLayers());