UI impl side painting default on

content/renderer/render_thread_impl.cc

Index: content/renderer/render_thread_impl.cc
diff --git a/content/renderer/render_thread_impl.cc b/content/renderer/render_thread_impl.cc
index 35bd5e3f4e6f931153c499fdd4310855ce83febd..970f6e844a0e27121471190be58f0afd6a04e8c8 100644
--- a/content/renderer/render_thread_impl.cc
+++ b/content/renderer/render_thread_impl.cc
@@ -669,7 +669,12 @@ void RenderThreadImpl::Init() {
     // 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(