Reapply "Add a switch to enable composited scrolling for frames and enable it on Android"

webkit/glue/webpreferences.cc

Index: webkit/glue/webpreferences.cc
diff --git a/webkit/glue/webpreferences.cc b/webkit/glue/webpreferences.cc
index 13e5c519d8c40c9093d523192ab49b8fb390ec52..7c783fb87eb1d254d02dfd50994b53fd8e408a7d 100644
--- a/webkit/glue/webpreferences.cc
+++ b/webkit/glue/webpreferences.cc
@@ -85,6 +85,7 @@ WebPreferences::WebPreferences()
       show_fps_counter(false),
       accelerated_compositing_for_overflow_scroll_enabled(false),
       accelerated_compositing_for_scrollable_frames_enabled(false),
+      composited_scrolling_for_frames_enabled(false),
       show_paint_rects(false),
       render_vsync_enabled(true),
       asynchronous_spell_checking_enabled(true),
@@ -364,6 +365,10 @@ void WebPreferences::Apply(WebView* web_view) const {
   settings->setAcceleratedCompositingForScrollableFramesEnabled(
       accelerated_compositing_for_scrollable_frames_enabled);
 
+  // Enables composited scrolling for frames if requested on command line.
+  settings->setCompositedScrollingForFramesEnabled(
+      composited_scrolling_for_frames_enabled);
+
   // Display the current compositor tree as overlay if requested on
   // the command line
   settings->setShowPlatformLayerTree(show_composited_layer_tree);