UI impl side painting default on

content/renderer/render_thread_impl.cc

 // Copyright (c) 2012 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 "content/renderer/render_thread_impl.h"
 
 #include <algorithm>
 #include <limits>
 #include <map>
 #include <vector>
@@ skipping 651 matching lines @@
     bool parsed_num_raster_threads =
         base::StringToInt(string_value, &num_raster_threads);
     DCHECK(parsed_num_raster_threads) << string_value;
     DCHECK_GT(num_raster_threads, 0);
 
     // Force maximum 1 thread for threaded GPU rasterization.
     // TODO(vmiura): crbug.com/459760 Support existence of multiple raster
     // threads in GPU raster mode.
     if (is_threaded_gpu_rasterization_enabled_)
       num_raster_threads = 1;
-    cc::TileTaskWorkerPool::SetNumWorkerThreads(num_raster_threads);
+
+    // In single process, browser compositor already initialized and set up
+    // worker threads, can't change the number later for the renderer compistor
+    // in the same process.
+    if (!command_line.HasSwitch(switches::kSingleProcess))

[enne (OOO), 2015/03/02 22:01:27]

danakj also suggests via proxy enne that this could be landed separately ahead
of time too.

That keeps the "turn it on" patch really simple.

[weiliangc, 2015/03/02 22:37:22]

https://codereview.chromium.org/971943002/

+      cc::TileTaskWorkerPool::SetNumWorkerThreads(num_raster_threads);
 
 #if defined(OS_ANDROID) || defined(OS_LINUX)
     if (!command_line.HasSwitch(
             switches::kUseNormalPriorityForTileTaskWorkerThreads)) {
       cc::TileTaskWorkerPool::SetWorkerThreadPriority(
           base::kThreadPriority_Background);
     }
 #endif
   }
 
@@ skipping 1144 matching lines @@
     mojo::InterfaceRequest<mojo::ServiceProvider> services,
     mojo::ServiceProviderPtr exposed_services)
     : services(services.Pass()),
       exposed_services(exposed_services.Pass()) {
 }
 
 RenderThreadImpl::PendingRenderFrameConnect::~PendingRenderFrameConnect() {
 }
 
 }  // namespace content