Track whether a scroll sequence has been partially prevented

content/common/input/web_input_event_traits.cc

 // Copyright 2013 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/common/input/web_input_event_traits.h"
 
 #include <bitset>
 #include <limits>
 
 #include "base/logging.h"
@@ skipping 247 matching lines @@
 }
 
 void Coalesce(const WebGestureEvent& event_to_coalesce,
               WebGestureEvent* event) {
   DCHECK(CanCoalesce(event_to_coalesce, *event));
   if (event->type == WebInputEvent::GestureScrollUpdate) {
     event->data.scrollUpdate.deltaX +=
         event_to_coalesce.data.scrollUpdate.deltaX;
     event->data.scrollUpdate.deltaY +=
         event_to_coalesce.data.scrollUpdate.deltaY;
+    DCHECK_EQ(
+        event->data.scrollUpdate.previousUpdateInSequencePrevented,
+        event_to_coalesce.data.scrollUpdate.previousUpdateInSequencePrevented);
   } else if (event->type == WebInputEvent::GesturePinchUpdate) {
     event->data.pinchUpdate.scale *= event_to_coalesce.data.pinchUpdate.scale;
     // Ensure the scale remains bounded above 0 and below Infinity so that
     // we can reliably perform operations like log on the values.
     if (event->data.pinchUpdate.scale < numeric_limits<float>::min())
       event->data.pinchUpdate.scale = numeric_limits<float>::min();
     else if (event->data.pinchUpdate.scale > numeric_limits<float>::max())
       event->data.pinchUpdate.scale = numeric_limits<float>::max();
   }
 }
@@ skipping 195 matching lines @@
     case WebInputEvent::TouchStart:
     case WebInputEvent::TouchMove:
     case WebInputEvent::TouchEnd:
       return !static_cast<const WebTouchEvent&>(event).cancelable;
     default:
       return false;
   }
 }
 
 }  // namespace content