Animated scroll shouldn't consume unhandled scrolls for OOPIFs.

content/browser/renderer_host/render_widget_host_impl.cc

Index: content/browser/renderer_host/render_widget_host_impl.cc
diff --git a/content/browser/renderer_host/render_widget_host_impl.cc b/content/browser/renderer_host/render_widget_host_impl.cc
index 8f605720ea04f61beb112b06d549c9a302687407..9ff92bea0eb221a57d145259c982008bd3a09208 100644
--- a/content/browser/renderer_host/render_widget_host_impl.cc
+++ b/content/browser/renderer_host/render_widget_host_impl.cc
@@ -1101,11 +1101,13 @@ void RenderWidgetHostImpl::ForwardGestureEventWithLatencyInfo(
               blink::WebGestureDevice::kWebGestureDeviceTouchpad
           ? &is_in_touchpad_gesture_scroll_
           : &is_in_touchscreen_gesture_scroll_;
-  if (gesture_event.GetType() == blink::WebInputEvent::kGestureScrollBegin) {
+  if (gesture_event.GetType() == blink::WebInputEvent::kGestureScrollBegin &&
+      !gesture_event.data.scroll_begin.synthetic) {
     DCHECK(!(*is_in_gesture_scroll));
     *is_in_gesture_scroll = true;
-  } else if (gesture_event.GetType() ==
-                 blink::WebInputEvent::kGestureScrollEnd ||
+  } else if ((gesture_event.GetType() ==
+                  blink::WebInputEvent::kGestureScrollEnd &&
+              !gesture_event.data.scroll_end.synthetic) ||
              gesture_event.GetType() ==
                  blink::WebInputEvent::kGestureFlingStart) {
     // TODO(wjmaclean): Re-enable the following DCHECK once crbug.com/695187
@@ -1147,6 +1149,19 @@ void RenderWidgetHostImpl::ForwardGestureEventWithLatencyInfo(
   }
 }
 
+bool RenderWidgetHostImpl::is_in_gesture_scroll(
+    blink::WebGestureDevice device) {
+  switch (device) {
+    case blink::WebGestureDevice::kWebGestureDeviceTouchpad:
+      return is_in_touchpad_gesture_scroll_;
+    case blink::WebGestureDevice::kWebGestureDeviceTouchscreen:
+      return is_in_touchscreen_gesture_scroll_;
+    default:
+      NOTREACHED();
+      return false;  // Required to keep the compiler happy.
+  }
+}
+
 void RenderWidgetHostImpl::ForwardEmulatedTouchEvent(
       const blink::WebTouchEvent& touch_event) {
   TRACE_EVENT0("input", "RenderWidgetHostImpl::ForwardEmulatedTouchEvent");