Re-land: cc: Implement shared worker contexts.

cc/trees/single_thread_proxy.cc

Index: cc/trees/single_thread_proxy.cc
diff --git a/cc/trees/single_thread_proxy.cc b/cc/trees/single_thread_proxy.cc
index 8ab3bc272403321e277ea26dd450517350247d7a..cefc0748ad15f6f6cac702a1d4f006ebc82747b7 100644
--- a/cc/trees/single_thread_proxy.cc
+++ b/cc/trees/single_thread_proxy.cc
@@ -149,7 +149,7 @@ void SingleThreadProxy::RequestNewOutputSurface() {
   layer_tree_host_->RequestNewOutputSurface();
 }
 
-scoped_ptr<OutputSurface> SingleThreadProxy::ReleaseOutputSurface() {
+void SingleThreadProxy::ReleaseOutputSurface() {
   // |layer_tree_host_| should already be aware of this.
   DCHECK(layer_tree_host_->output_surface_lost());
 
@@ -158,8 +158,7 @@ scoped_ptr<OutputSurface> SingleThreadProxy::ReleaseOutputSurface() {
   return layer_tree_host_impl_->ReleaseOutputSurface();
 }
 
-void SingleThreadProxy::SetOutputSurface(
-    scoped_ptr<OutputSurface> output_surface) {
+void SingleThreadProxy::SetOutputSurface(OutputSurface* output_surface) {
   DCHECK(Proxy::IsMainThread());
   DCHECK(layer_tree_host_->output_surface_lost());
   DCHECK(output_surface_creation_requested_);
@@ -169,7 +168,7 @@ void SingleThreadProxy::SetOutputSurface(
   {
     DebugScopedSetMainThreadBlocked main_thread_blocked(this);
     DebugScopedSetImplThread impl(this);
-    success = layer_tree_host_impl_->InitializeRenderer(output_surface.Pass());
+    success = layer_tree_host_impl_->InitializeRenderer(output_surface);
   }
 
   if (success) {