Filter GestureFlingStarts with Vx=Vy=0 in RenderWidgetHostViewChildFrame

content/browser/renderer_host/render_widget_host_view_aura.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/renderer_host/render_widget_host_view_aura.h"
 
 #include <set>
 #include <utility>
 
 #include "base/auto_reset.h"
@@ skipping 1298 matching lines @@
     }
   }
 
   if (overscroll_controller_)
     consumed |= overscroll_controller_->WillHandleEvent(input_event);
 
   // Touch events should always propagate to the renderer.
   if (WebTouchEvent::isTouchEventType(input_event.type))
     return INPUT_EVENT_ACK_STATE_NOT_CONSUMED;
 
-  // Reporting consumed for a fling suggests that there's now an *active* fling
-  // that requires both animation and a fling-end notification. However, the
-  // OverscrollController consumes a fling to stop its propagation; it doesn't
-  // actually tick a fling animation. Report no consumer to convey this.
-  if (consumed && input_event.type == blink::WebInputEvent::GestureFlingStart)
+  if (consumed && input_event.type == blink::WebInputEvent::GestureFlingStart) {
+    // 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: Similar code exists in
+    // RenderWidgetHostViewChildFrame::FilterInputEvent()
     return INPUT_EVENT_ACK_STATE_NO_CONSUMER_EXISTS;
+  }
 
   return consumed ? INPUT_EVENT_ACK_STATE_CONSUMED
                   : INPUT_EVENT_ACK_STATE_NOT_CONSUMED;
 }
 
 BrowserAccessibilityManager*
 RenderWidgetHostViewAura::CreateBrowserAccessibilityManager(
     BrowserAccessibilityDelegate* delegate, bool for_root_frame) {
   BrowserAccessibilityManager* manager = NULL;
 #if defined(OS_WIN)
@@ skipping 1702 matching lines @@
 
 ////////////////////////////////////////////////////////////////////////////////
 // RenderWidgetHostViewBase, public:
 
 // static
 void RenderWidgetHostViewBase::GetDefaultScreenInfo(WebScreenInfo* results) {
   GetScreenInfoForWindow(results, NULL);
 }
 
 }  // namespace content