Add feature for main frame before activation.

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 5924ede574d798e572f8a8325f11c1e58b5ef25e..6dc1944f98381ef9b9215dbc9db55aee41af290c 100644
--- a/content/browser/renderer_host/render_process_host_impl.cc
+++ b/content/browser/renderer_host/render_process_host_impl.cc
@@ -1241,6 +1241,9 @@ static void AppendCompositorCommandLineFlags(base::CommandLine* command_line) {
         switches::kEnableGpuMemoryBufferCompositorResources);
   }
 
+  if (IsMainFrameBeforeActivationEnabled())
+    command_line->AppendSwitch(cc::switches::kEnableMainFrameBeforeActivation);
+
   // Persistent buffers may come at a performance hit (not all platform specific
   // buffers support it), so only enable them if partial raster is enabled and
   // we are actually going to use them.
@@ -1468,12 +1471,10 @@ void RenderProcessHostImpl::PropagateBrowserCommandLineToRenderer(
     // also be added to chrome/browser/chromeos/login/chrome_restart_request.cc.
     cc::switches::kDisableCachedPictureRaster,
     cc::switches::kDisableCompositedAntialiasing,
-    cc::switches::kDisableMainFrameBeforeActivation,
     cc::switches::kDisableThreadedAnimation,
     cc::switches::kEnableBeginFrameScheduling,
     cc::switches::kEnableGpuBenchmarking,
     cc::switches::kEnableLayerLists,
-    cc::switches::kEnableMainFrameBeforeActivation,
     cc::switches::kEnableTileCompression,
     cc::switches::kShowCompositedLayerBorders,
     cc::switches::kShowFPSCounter,