Revert of cc: Implement shared worker contexts.

cc/trees/layer_tree_host_impl.cc

Index: cc/trees/layer_tree_host_impl.cc
diff --git a/cc/trees/layer_tree_host_impl.cc b/cc/trees/layer_tree_host_impl.cc
index 45cd0c8b4e809780b8779247ecd53aeea3aa2be2..a7af98350fd28eef53eb393b8b3b37f2b268f78c 100644
--- a/cc/trees/layer_tree_host_impl.cc
+++ b/cc/trees/layer_tree_host_impl.cc
@@ -172,7 +172,6 @@
     : client_(client),
       proxy_(proxy),
       current_begin_frame_tracker_(BEGINFRAMETRACKER_FROM_HERE),
-      output_surface_(nullptr),
       content_is_suitable_for_gpu_rasterization_(true),
       has_gpu_rasterization_trigger_(false),
       use_gpu_rasterization_(false),
@@ -286,13 +285,6 @@
   }
 
   CleanUpTileManager();
-  renderer_ = nullptr;
-  resource_provider_ = nullptr;
-
-  if (output_surface_) {
-    output_surface_->DetachFromClient();
-    output_surface_ = nullptr;
-  }
 }
 
 void LayerTreeHostImpl::BeginMainFrameAborted(CommitEarlyOutReason reason) {
@@ -1570,7 +1562,7 @@
 
     scoped_ptr<SoftwareRenderer> temp_software_renderer =
         SoftwareRenderer::Create(this, &settings_.renderer_settings,
-                                 output_surface_, NULL);
+                                 output_surface_.get(), NULL);
     temp_software_renderer->DrawFrame(&frame->render_passes,
                                       device_scale_factor_,
                                       DeviceViewport(),
@@ -1632,7 +1624,7 @@
 
   ContextProvider* context_provider =
       output_surface_->worker_context_provider();
-  ContextProvider::ScopedContextLock scoped_context(context_provider);
+  base::AutoLock context_lock(*context_provider->GetLock());
   if (!context_provider->GrContext())
     return false;
 
@@ -2016,18 +2008,18 @@
   DCHECK(resource_provider_);
 
   if (output_surface_->capabilities().delegated_rendering) {
-    renderer_ =
-        DelegatingRenderer::Create(this, &settings_.renderer_settings,
-                                   output_surface_, resource_provider_.get());
+    renderer_ = DelegatingRenderer::Create(this, &settings_.renderer_settings,
+                                           output_surface_.get(),
+                                           resource_provider_.get());
   } else if (output_surface_->context_provider()) {
     renderer_ = GLRenderer::Create(
-        this, &settings_.renderer_settings, output_surface_,
+        this, &settings_.renderer_settings, output_surface_.get(),
         resource_provider_.get(), texture_mailbox_deleter_.get(),
         settings_.renderer_settings.highp_threshold_min);
   } else if (output_surface_->software_device()) {
-    renderer_ =
-        SoftwareRenderer::Create(this, &settings_.renderer_settings,
-                                 output_surface_, resource_provider_.get());
+    renderer_ = SoftwareRenderer::Create(this, &settings_.renderer_settings,
+                                         output_surface_.get(),
+                                         resource_provider_.get());
   }
   DCHECK(renderer_);
 
@@ -2156,7 +2148,8 @@
   single_thread_synchronous_task_graph_runner_ = nullptr;
 }
 
-bool LayerTreeHostImpl::InitializeRenderer(OutputSurface* output_surface) {
+bool LayerTreeHostImpl::InitializeRenderer(
+    scoped_ptr<OutputSurface> output_surface) {
   TRACE_EVENT0("cc", "LayerTreeHostImpl::InitializeRenderer");
 
   // Since we will create a new resource provider, we cannot continue to use
@@ -2168,14 +2161,7 @@
   renderer_ = nullptr;
   CleanUpTileManager();
   resource_provider_ = nullptr;
-
-  // Detach from the old output surface and reset |output_surface_| pointer
-  // as this surface is going to be destroyed independent of if binding the
-  // new output surface succeeds or not.
-  if (output_surface_) {
-    output_surface_->DetachFromClient();
-    output_surface_ = nullptr;
-  }
+  output_surface_ = nullptr;
 
   if (!output_surface->BindToClient(this)) {
     // Avoid recreating tree resources because we might not have enough
@@ -2184,9 +2170,9 @@
     return false;
   }
 
-  output_surface_ = output_surface;
+  output_surface_ = output_surface.Pass();
   resource_provider_ = ResourceProvider::Create(
-      output_surface_, shared_bitmap_manager_, gpu_memory_buffer_manager_,
+      output_surface_.get(), shared_bitmap_manager_, gpu_memory_buffer_manager_,
       proxy_->blocking_main_thread_task_runner(),
       settings_.renderer_settings.highp_threshold_min,
       settings_.renderer_settings.use_rgba_4444_textures,