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

content/public/common/content_switches.cc

Index: content/public/common/content_switches.cc
diff --git a/content/public/common/content_switches.cc b/content/public/common/content_switches.cc
index cf0b4db5a53c025133ba23235bde963e1cc98fc8..7af9f2a2b8c1821c4ed730790092aa5b5dedde82 100644
--- a/content/public/common/content_switches.cc
+++ b/content/public/common/content_switches.cc
@@ -588,10 +588,15 @@ const char kEnableAcceleratedOverflowScroll[] =
     "enable-accelerated-overflow-scroll";
 
 // Enables accelerated compositing for scrollable frames for accelerated
-// scrolling for them.
+// scrolling for them. Requires kForceCompositingMode.
 const char kEnableAcceleratedScrollableFrames[] =
      "enable-accelerated-scrollable-frames";
 
+// Enables accelerated scrolling by the compositor for frames. Requires
+// kForceCompositingMode and kEnableAcceleratedScrollableFrames.
+const char kEnableCompositedScrollingForFrames[] =
+     "enable-composited-scrolling-for-frames";
+
 // Visibly render a border around paint rects in the web page to help debug
 // and study painting behavior.
 const char kShowPaintRects[]                = "show-paint-rects";