Plumb smooth scrolling in Chromium compositor

content/common/input/gesture_event_stream_validator.cc

Index: content/common/input/gesture_event_stream_validator.cc
diff --git a/content/common/input/gesture_event_stream_validator.cc b/content/common/input/gesture_event_stream_validator.cc
index 6ea29de25ac8536fd054b45af307ee58dc5cdebe..1a8985874b92ca048fad9bce855deede3c8b4315 100644
--- a/content/common/input/gesture_event_stream_validator.cc
+++ b/content/common/input/gesture_event_stream_validator.cc
@@ -40,12 +40,19 @@ bool GestureEventStreamValidator::Validate(const blink::WebGestureEvent& event,
       if (!scrolling_)
         error_msg->append("Scroll update outside of scroll\n");
       break;
+    // add validators for smoothscroll
     case WebInputEvent::GestureFlingStart:
       if (event.sourceDevice == blink::WebGestureDeviceTouchscreen &&
           !event.data.flingStart.velocityX &&
-          !event.data.flingStart.velocityY) {
+          !event.data.flingStart.velocityY &&
+          !event.data.flingStart.isSmoothScroll) {
         error_msg->append("Zero velocity touchscreen fling\n");
       }
+      if (event.sourceDevice == blink::WebGestureDeviceTouchscreen &&
+          event.data.flingStart.isSmoothScroll && !event.data.flingStart.dx &&
+          !event.data.flingStart.dy) {
+        error_msg->append("Zero distance smooth scroll\n");
+      }
       if (!scrolling_)
         error_msg->append("Fling start outside of scroll\n");
       if (pinching_)