cc: Get rid of LayerTreeHost::output_surface_lost_ state.

cc/trees/layer_tree_host_impl.cc

 // Copyright 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/trees/layer_tree_host_impl.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 2315 matching lines @@
   tile_manager_.FinishTasksAndCleanUp();
   resource_pool_ = nullptr;
   tile_task_manager_ = nullptr;
   single_thread_synchronous_task_graph_runner_ = nullptr;
   image_decode_controller_ = nullptr;
 }
 
 void LayerTreeHostImpl::ReleaseOutputSurface() {
   TRACE_EVENT0("cc", "LayerTreeHostImpl::ReleaseOutputSurface");
 
+  if (!output_surface_)
+    return;
+
   // Since we will create a new resource provider, we cannot continue to use
   // the old resources (i.e. render_surfaces and texture IDs). Clear them
   // before we destroy the old resource provider.
   ReleaseTreeResources();
 
   // Note: order is important here.
   renderer_ = nullptr;
   CleanUpTileManagerAndUIResources();
   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_->DetachFromClient();
+  output_surface_ = nullptr;
 
   // We don't know if the next OutputSurface will support GPU rasterization.
   // Make sure to clear the flag so that we force a re-computation.
   use_gpu_rasterization_ = false;
 }
 
 bool LayerTreeHostImpl::InitializeRenderer(OutputSurface* output_surface) {
   TRACE_EVENT0("cc", "LayerTreeHostImpl::InitializeRenderer");
 
   ReleaseOutputSurface();
@@ skipping 1819 matching lines @@
   return task_runner_provider_->HasImplThread();
 }
 
 bool LayerTreeHostImpl::CommitToActiveTree() const {
   // In single threaded mode we skip the pending tree and commit directly to the
   // active tree.
   return !task_runner_provider_->HasImplThread();
 }
 
 }  // namespace cc