Re-land: cc: Implement shared worker contexts.

cc/test/layer_tree_test.cc

Index: cc/test/layer_tree_test.cc
diff --git a/cc/test/layer_tree_test.cc b/cc/test/layer_tree_test.cc
index c87c36b780ba0f07a8008cf00a459ca8e131013d..e2d19b0f43e0a21763dc69334158430bb4f8f582 100644
--- a/cc/test/layer_tree_test.cc
+++ b/cc/test/layer_tree_test.cc
@@ -404,8 +404,8 @@ class LayerTreeHostImplForTesting : public LayerTreeHostImpl {
     test_hooks_->DidActivateTreeOnThread(this);
   }
 
-  bool InitializeRenderer(scoped_ptr<OutputSurface> output_surface) override {
-    bool success = LayerTreeHostImpl::InitializeRenderer(output_surface.Pass());
+  bool InitializeRenderer(OutputSurface* output_surface) override {
+    bool success = LayerTreeHostImpl::InitializeRenderer(output_surface);
     test_hooks_->InitializedRendererOnThread(this, success);
     return success;
   }