Add a flag for enabling/disabling the new accelerated scrolling path

content/renderer/render_view_impl.cc

Index: content/renderer/render_view_impl.cc
diff --git a/content/renderer/render_view_impl.cc b/content/renderer/render_view_impl.cc
index 4dbe32cd592a1d7f8ae2deab1bb8db601fbe1a15..10a4abc6ec8eb0cbea8608a93542b9c58e2e427d 100644
--- a/content/renderer/render_view_impl.cc
+++ b/content/renderer/render_view_impl.cc
@@ -602,6 +602,20 @@ static bool ShouldUseAcceleratedCompositingForOverflowScroll(
   return DeviceScaleEnsuresTextQuality(device_scale_factor);
 }
 
+static bool ShouldUseUniversalAcceleratedCompositingForOverflowScroll() {

[darin (slow to review), 2013/10/11 04:58:13]

Impressive function name!

+  const CommandLine& command_line = *CommandLine::ForCurrentProcess();
+
+  if (command_line.HasSwitch(
+          switches::kDisableUniversalAcceleratedOverflowScroll))
+    return false;
+
+  if (command_line.HasSwitch(
+          switches::kEnableUniversalAcceleratedOverflowScroll))
+    return true;
+
+  return false;
+}
+
 static bool ShouldUseAcceleratedCompositingForScrollableFrames(
     float device_scale_factor) {
   const CommandLine& command_line = *CommandLine::ForCurrentProcess();
@@ -923,6 +937,8 @@ void RenderViewImpl::Initialize(RenderViewImplParams* params) {
       ShouldUseFixedPositionCompositing(device_scale_factor_));
   webview()->settings()->setAcceleratedCompositingForOverflowScrollEnabled(
       ShouldUseAcceleratedCompositingForOverflowScroll(device_scale_factor_));
+  webview()->settings()->setCompositorDrivenAcceleratedScrollingEnabled(
+      ShouldUseUniversalAcceleratedCompositingForOverflowScroll());
   webview()->settings()->setAcceleratedCompositingForTransitionEnabled(
       ShouldUseTransitionCompositing(device_scale_factor_));
   webview()->settings()->setAcceleratedCompositingForFixedRootBackgroundEnabled(