Filter GestureFlingStarts with Vx=Vy=0 in RenderWidgetHostViewChildFrame

content/browser/frame_host/render_widget_host_view_child_frame.cc

Index: content/browser/frame_host/render_widget_host_view_child_frame.cc
diff --git a/content/browser/frame_host/render_widget_host_view_child_frame.cc b/content/browser/frame_host/render_widget_host_view_child_frame.cc
index 09f1353e453a7a173507f4aff28078083853de7d..8fbfdc163d3866366f5a4d5027a5b26eae854068 100644
--- a/content/browser/frame_host/render_widget_host_view_child_frame.cc
+++ b/content/browser/frame_host/render_widget_host_view_child_frame.cc
@@ -33,6 +33,7 @@
 #include "content/public/browser/render_process_host.h"
 #include "content/public/common/browser_plugin_guest_mode.h"
 #include "gpu/ipc/common/gpu_messages.h"
+#include "third_party/WebKit/public/web/WebInputEvent.h"
 #include "ui/gfx/geometry/size_conversions.h"
 #include "ui/gfx/geometry/size_f.h"
 
@@ -655,6 +656,31 @@ void RenderWidgetHostViewChildFrame::OnSetNeedsBeginFrames(
   }
 }
 
+InputEventAckState RenderWidgetHostViewChildFrame::FilterInputEvent(
+    const blink::WebInputEvent& input_event) {
+  if (input_event.type == blink::WebInputEvent::GestureFlingStart) {
+    const blink::WebGestureEvent& gesture_event =
+        static_cast<const blink::WebGestureEvent&>(input_event);
+    // Zero-velocity touchpad flings are an Aura-specific signal that the
+    // touchpad scroll has ended, and should not be forwarded to the renderer.
+    if (gesture_event.sourceDevice == blink::WebGestureDeviceTouchpad &&
+        !gesture_event.data.flingStart.velocityX &&
+        !gesture_event.data.flingStart.velocityY) {
+      // Here we indicate that there was no consumer for this event, as
+      // otherwise the fling animation system will try to run an animation
+      // and will also expect a notification when the fling ends. Since
+      // CrOS just uses the GestureFlingStart with zero-velocity as a means
+      // of indicating that touchpad scroll has ended, we don't actually want
+      // a fling animation.
+      // Note: this event handling is modeled on similar code in
+      // TenderWidgetHostViewAura::FilterInputEvent().
+      return INPUT_EVENT_ACK_STATE_NO_CONSUMER_EXISTS;
+    }
+  }
+
+  return INPUT_EVENT_ACK_STATE_NOT_CONSUMED;
+}
+
 BrowserAccessibilityManager*
 RenderWidgetHostViewChildFrame::CreateBrowserAccessibilityManager(
     BrowserAccessibilityDelegate* delegate, bool for_root_frame) {