Articulate the cancel behavior in the WebTouchEvent.

content/browser/renderer_host/input/input_router_impl.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/browser/renderer_host/input/input_router_impl.h"
 
 #include <math.h>
 #include <utility>
 
 #include "base/auto_reset.h"
@@ skipping 350 matching lines @@
   OfferToHandlers(input_event, latency_info);
 }
 
 void InputRouterImpl::OfferToHandlers(const WebInputEvent& input_event,
                                       const ui::LatencyInfo& latency_info) {
   output_stream_validator_.Validate(input_event);
 
   if (OfferToClient(input_event, latency_info))
     return;
 
-  // Touch events should always indicate in the event whether they are
-  // cancelable (respect ACK disposition) or not except touchmove.
   bool should_block = WebInputEventTraits::ShouldBlockEventStream(input_event);
-
   OfferToRenderer(input_event, latency_info,
                   should_block
                       ? InputEventDispatchType::DISPATCH_TYPE_BLOCKING
                       : InputEventDispatchType::DISPATCH_TYPE_NON_BLOCKING);
 
   if (WebInputEvent::isTouchEventType(input_event.type) &&
       input_event.type != WebInputEvent::TouchMove) {
     const WebTouchEvent& touch = static_cast<const WebTouchEvent&>(input_event);
     DCHECK_EQ(should_block, touch.cancelable);
   }
@@ skipping 257 matching lines @@
 
   flush_requested_ = false;
   client_->DidFlush();
 }
 
 void InputRouterImpl::SetFrameTreeNodeId(int frameTreeNodeId) {
   frame_tree_node_id_ = frameTreeNodeId;
 }
 
 }  // namespace content