compositor-worker: Introduce WebCompositorMutableState

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 aa2a2b578621b197ef8bfb5745e430fad448aa9a..228e19227a5564ead2d3ad113043e0de4c7c48a3 100644
--- a/cc/layers/layer_impl.cc
+++ b/cc/layers/layer_impl.cc
@@ -106,6 +106,10 @@ LayerImpl::LayerImpl(LayerTreeImpl* tree_impl,
       layer_animation_controller_->set_layer_animation_delegate(this);
     }
   }
+
+  if (element_id_)
+    layer_tree_impl_->AddToElementMap(this);
+
   SetNeedsPushProperties();
 }
 
@@ -123,6 +127,9 @@ LayerImpl::~LayerImpl() {
   layer_tree_impl_->UnregisterScrollLayer(this);
   layer_tree_impl_->UnregisterLayer(this);
 
+  if (element_id_)
+    layer_tree_impl_->RemoveFromElementMap(this);
+
   TRACE_EVENT_OBJECT_DELETED_WITH_ID(
       TRACE_DISABLED_BY_DEFAULT("cc.debug"), "cc::LayerImpl", this);
 }
@@ -1219,7 +1226,11 @@ void LayerImpl::SetElementId(uint64_t element_id) {
   TRACE_EVENT1(TRACE_DISABLED_BY_DEFAULT("compositor-worker"),
                "LayerImpl::SetElementId", "id", element_id);
 
+  if (element_id_)
+    layer_tree_impl_->RemoveFromElementMap(this);
   element_id_ = element_id;
+  if (element_id_)
+    layer_tree_impl_->AddToElementMap(this);
   SetNeedsPushProperties();
 }
 
@@ -1231,6 +1242,10 @@ void LayerImpl::SetMutableProperties(uint32_t properties) {
                "LayerImpl::SetMutableProperties", "properties", properties);
 
   mutable_properties_ = properties;
+  // If this layer is already in the element map, we will add it again in order
+  // to update the layer assignments per these new properties.
+  if (element_id_)
+    layer_tree_impl_->AddToElementMap(this);
   SetNeedsPushProperties();
 }