Cancel drag operation when the tab RenderWidgetHostView does not exist (Mac)

content/browser/renderer_host/render_widget_host_input_event_router.cc

 // Copyright 2015 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_input_event_router.h"
 
 #include <vector>
 
 #include "base/metrics/histogram_macros.h"
 
@@ skipping 631 matching lines @@
   HittestData data;
   data.ignored_for_hittest = params.ignored_for_hittest;
   hittest_data_[params.surface_id] = data;
 }
 
 RenderWidgetHostImpl*
 RenderWidgetHostInputEventRouter::GetRenderWidgetHostAtPoint(
     RenderWidgetHostViewBase* root_view,
     const gfx::Point& point,
     gfx::Point* transformed_point) {
+  if (!root_view)
+    return nullptr;
   return RenderWidgetHostImpl::From(
       FindEventTarget(root_view, point, transformed_point)
           ->GetRenderWidgetHost());
 }
 
 void RenderWidgetHostInputEventRouter::RouteTouchscreenGestureEvent(
     RenderWidgetHostViewBase* root_view,
     blink::WebGestureEvent* event,
     const ui::LatencyInfo& latency) {
   DCHECK_EQ(blink::WebGestureDeviceTouchscreen, event->sourceDevice);
@@ skipping 109 matching lines @@
   if (!touchpad_gesture_target_.target)
     return;
 
   // TODO(mohsen): Add tests to check event location.
   event->x += touchpad_gesture_target_.delta.x();
   event->y += touchpad_gesture_target_.delta.y();
   touchpad_gesture_target_.target->ProcessGestureEvent(*event, latency);
 }
 
 }  // namespace content