Revert of Remove EnableThreadedCompositing from the browser.

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 0ad5ecac1faff03462bb68bf560c7184756fc3df..890c3909dcb984dfadc7191765722edf3166df40 100644
--- a/content/browser/renderer_host/render_process_host_impl.cc
+++ b/content/browser/renderer_host/render_process_host_impl.cc
@@ -1003,6 +1003,9 @@
   if (IsPinchVirtualViewportEnabled())
     command_line->AppendSwitch(cc::switches::kEnablePinchVirtualViewport);
 
+  if (IsThreadedCompositingEnabled())
+    command_line->AppendSwitch(switches::kEnableThreadedCompositing);
+
   if (IsDelegatedRendererEnabled())
     command_line->AppendSwitch(switches::kEnableDelegatedRenderer);
 
@@ -1105,7 +1108,6 @@
     switches::kDisableSeccompFilterSandbox,
     switches::kDisableSessionStorage,
     switches::kDisableSharedWorkers,
-    switches::kDisableThreadedCompositing,
     switches::kDisableTouchAdjustment,
     switches::kDisableTouchDragDrop,
     switches::kDisableTouchEditing,
@@ -1152,6 +1154,7 @@
     switches::kEnableTouchEditing,
     switches::kEnableViewport,
     switches::kEnableViewportMeta,
+    switches::kMainFrameResizesAreOrientationChanges,
     switches::kEnableVtune,
     switches::kEnableWebAnimationsSVG,
     switches::kEnableWebGLDraftExtensions,
@@ -1163,7 +1166,6 @@
     switches::kIgnoreResolutionLimitsForAcceleratedVideoDecode,
     switches::kJavaScriptFlags,
     switches::kLoggingLevel,
-    switches::kMainFrameResizesAreOrientationChanges,
     switches::kMaxUntiledLayerWidth,
     switches::kMaxUntiledLayerHeight,
     switches::kMemoryMetrics,