Forward GestureFlingStart in OOPIF, re-enable DCHECK.

content/browser/frame_host/render_widget_host_view_child_frame.cc

 // Copyright 2014 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/frame_host/render_widget_host_view_child_frame.h"
 
 #include <algorithm>
 #include <utility>
 #include <vector>
 
@@ skipping 325 matching lines @@
   // GestureScrollBegin is consumed by the target frame and not forwarded,
   // because we don't know whether we will need to bubble scroll until we
   // receive a GestureScrollUpdate ACK. GestureScrollUpdate with unused
   // scroll extent is forwarded for bubbling, while GestureScrollEnd is
   // always forwarded and handled according to current scroll state in the
   // RenderWidgetHostInputEventRouter.
   if (!frame_connector_)
     return;
   if ((event.GetType() == blink::WebInputEvent::kGestureScrollUpdate &&
        not_consumed) ||
-      event.GetType() == blink::WebInputEvent::kGestureScrollEnd)
+      event.GetType() == blink::WebInputEvent::kGestureScrollEnd ||
+      event.GetType() == blink::WebInputEvent::kGestureFlingStart) {
     frame_connector_->BubbleScrollEvent(event);
+  }
 }
 
 void RenderWidgetHostViewChildFrame::DidReceiveCompositorFrameAck(
     const cc::ReturnedResourceArray& resources) {
   renderer_compositor_frame_sink_->DidReceiveCompositorFrameAck(resources);
 }
 
 void RenderWidgetHostViewChildFrame::DidCreateNewRendererCompositorFrameSink(
     cc::mojom::MojoCompositorFrameSinkClient* renderer_compositor_frame_sink) {
   ResetCompositorFrameSinkSupport();
@@ skipping 355 matching lines @@
                                                       frame_sink_id_);
   }
   support_.reset();
 }
 
 bool RenderWidgetHostViewChildFrame::HasEmbedderChanged() {
   return false;
 }
 
 }  // namespace content