Implements core logic for Pixel Canvas

ui/compositor/layer.cc

Index: ui/compositor/layer.cc
diff --git a/ui/compositor/layer.cc b/ui/compositor/layer.cc
index 6f2ac6c5b6a06c625c14d91316b7f104d99d4cf6..d436259ef739df50c3f939926db82124d50d3a7f 100644
--- a/ui/compositor/layer.cc
+++ b/ui/compositor/layer.cc
@@ -40,6 +40,10 @@
 namespace {
 
 const ui::Layer* GetRoot(const ui::Layer* layer) {
+  // Parent walk cannot be done on a layer that is being used as a mask. Get the
+  // layer to which this layer is a mask of.
+  if (layer->layer_mask_back_link())
+    layer = layer->layer_mask_back_link();
   while (layer->parent())
     layer = layer->parent();
   return layer;
@@ -315,7 +319,7 @@ void Layer::SetAnimator(LayerAnimator* animator) {
   Compositor* compositor = GetCompositor();
 
   if (animator_) {
-    if (compositor)
+    if (compositor && !layer_mask_back_link())
       animator_->DetachLayerAndTimeline(compositor);
     animator_->SetDelegate(nullptr);
   }
@@ -324,7 +328,7 @@ void Layer::SetAnimator(LayerAnimator* animator) {
 
   if (animator_) {
     animator_->SetDelegate(this);
-    if (compositor)
+    if (compositor && !layer_mask_back_link())
       animator_->AttachLayerAndTimeline(compositor);
   }
 }
@@ -943,8 +947,9 @@ scoped_refptr<cc::DisplayItemList> Layer::PaintContentsToDisplayList(
   paint_region_.Clear();
   auto display_list = make_scoped_refptr(new cc::DisplayItemList);
   if (delegate_) {
-    delegate_->OnPaintLayer(
-        PaintContext(display_list.get(), device_scale_factor_, invalidation));
+    delegate_->OnPaintLayer(PaintContext(display_list.get(),
+                                         device_scale_factor_, invalidation,
+                                         GetCompositor()->is_pixel_canvas()));
   }
   display_list->Finalize();
   // TODO(domlaskowski): Move mirror invalidation to Layer::SchedulePaint.