Make the number of raster threads appear in chrome://gpu.

content/browser/renderer_host/render_process_host_impl.cc

Index: content/browser/renderer_host/render_process_host_impl.cc
diff --git a/content/browser/renderer_host/render_process_host_impl.cc b/content/browser/renderer_host/render_process_host_impl.cc
index 0b95dda213f4478e756b8df802d049288b5f7398..8b80576124d26f3ebc00a0c562551506a0610271 100644
--- a/content/browser/renderer_host/render_process_host_impl.cc
+++ b/content/browser/renderer_host/render_process_host_impl.cc
@@ -1020,8 +1020,12 @@ static void AppendCompositorCommandLineFlags(base::CommandLine* command_line) {
   if (IsDelegatedRendererEnabled())
     command_line->AppendSwitch(switches::kEnableDelegatedRenderer);
 
-  if (IsImplSidePaintingEnabled())
+  if (IsImplSidePaintingEnabled()) {
     command_line->AppendSwitch(switches::kEnableImplSidePainting);
+    command_line->AppendSwitchASCII(
+        switches::kNumRasterThreads,
+        base::IntToString(NumberOfRendererRasterThreads()));
+  }
 
   if (content::IsGpuRasterizationEnabled())
     command_line->AppendSwitch(switches::kEnableGpuRasterization);
@@ -1179,7 +1183,6 @@ void RenderProcessHostImpl::PropagateBrowserCommandLineToRenderer(
     switches::kMemoryMetrics,
     switches::kNoReferrers,
     switches::kNoSandbox,
-    switches::kNumRasterThreads,

[Ken Russell (switch to Gerrit), 2014/08/29 22:41:05]

Why is this being removed from this list? Isn't it needed here to get this
argument propagated down to the renderer?

[danakj, 2014/08/29 22:42:20]

because the other code adds it to the renderer command line explicitly, we don't
just forward it along blindly. this list is flags to just copy from the browser
command line.

     switches::kPpapiInProcess,
     switches::kProfilerTiming,
     switches::kReduceSecurityForTesting,