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..e56caa10399423bdb2b065f0b7aca125ff186e80 100644
--- a/content/renderer/render_view_impl.cc
+++ b/content/renderer/render_view_impl.cc
@@ -602,6 +602,19 @@ static bool ShouldUseAcceleratedCompositingForOverflowScroll(
   return DeviceScaleEnsuresTextQuality(device_scale_factor);
 }
 
+static bool ShouldUseUniversalAcceleratedCompositingForOverflowScroll() {
+  const CommandLine& command_line = *CommandLine::ForCurrentProcess();
+
+  if (command_line.HasSwitch(
+          switches::kDisableUniversalAcceleratedOverflowScroll))

[shawnsingh, 2013/10/11 01:34:50]

wait!!!!

This code would compile, but seems pretty obvious there's a mistaken missing
condition here.

[Ian Vollick, 2013/10/11 01:38:59]

Whoa. Don't know how I missed this. Thanks for catching! Fixed.

+
+  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 +936,8 @@ 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(