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

chrome/app/generated_resources.grd

Index: chrome/app/generated_resources.grd
diff --git a/chrome/app/generated_resources.grd b/chrome/app/generated_resources.grd
index fff7c0ad6d01f1ff70164e92ffc0a1057ea96333..8e2fe3919d5ee6b708fe4651adfe8632bc0a8cf3 100644
--- a/chrome/app/generated_resources.grd
+++ b/chrome/app/generated_resources.grd
@@ -5722,6 +5722,12 @@ Keep your key file in a safe place. You will need it to create new versions of y
       <message name="IDS_FLAGS_FORCE_ACCELERATED_OVERFLOW_SCROLL_MODE_DESCRIPTION" desc="Description of the 'Accelerated overflow scroll mode' lab.">
         When possible, puts the scrolling contents of an overflow scrolling element onto a composited layer for faster scrolling.
       </message>
+      <message name="IDS_FLAGS_FORCE_UNIVERSAL_ACCELERATED_OVERFLOW_SCROLL_MODE_NAME" desc="Name of the 'Universal accelerated overflow scroll mode' lab.">
+        Universal accelerated overflow scroll
+      </message>
+      <message name="IDS_FLAGS_FORCE_UNIVERSAL_ACCELERATED_OVERFLOW_SCROLL_MODE_DESCRIPTION" desc="Description of the 'Universal accelerated overflow scroll mode' lab.">
+        Puts scrolling content in composited layers, even in those cases where promoting the overflow scrolling element to a stacking context and a containing block would have broken stacking or clipping.
+      </message>
       <message name="IDS_FLAGS_ENABLE_EXPERIMENTAL_CANVAS_FEATURES_NAME" desc="Name of the 'Enable experimental canvas features' lab.">
         Enable experimental canvas features
       </message>