Articulate the cancel behavior in the WebTouchEvent.

content/browser/renderer_host/input/touch_event_queue.cc

Index: content/browser/renderer_host/input/touch_event_queue.cc
diff --git a/content/browser/renderer_host/input/touch_event_queue.cc b/content/browser/renderer_host/input/touch_event_queue.cc
index b92b24aaa23e6efba589c23ce32705ab4feaeef7..7fb04c5d5986087819c4c205e8a1c764bec6077d 100644
--- a/content/browser/renderer_host/input/touch_event_queue.cc
+++ b/content/browser/renderer_host/input/touch_event_queue.cc
@@ -45,7 +45,7 @@ TouchEventWithLatencyInfo ObtainCancelEventForTouchEvent(
 bool ShouldTouchTriggerTimeout(const WebTouchEvent& event) {
   return (event.type == WebInputEvent::TouchStart ||
           event.type == WebInputEvent::TouchMove) &&
-         WebInputEventTraits::ShouldBlockEventStream(event) && event.cancelable;
+         event.dispatchType == WebInputEvent::Blocking;
 }
 
 // Compare all properties of touch points to determine the state.
@@ -509,6 +509,7 @@ void TouchEventQueue::PrependTouchScrollNotification() {
     touch.event.type = WebInputEvent::TouchScrollStarted;
     touch.event.uniqueTouchEventId = 0;
     touch.event.touchesLength = 0;
+    touch.event.dispatchType = WebInputEvent::EventNonBlocking;
 
     auto it = touch_queue_.begin();
     DCHECK(it != touch_queue_.end());
@@ -634,7 +635,9 @@ void TouchEventQueue::ForwardNextEventToRenderer() {
   if (pending_async_touchmove_) {
     if (pending_async_touchmove_->CanCoalesceWith(touch)) {
       pending_async_touchmove_->CoalesceWith(touch);
-      pending_async_touchmove_->event.cancelable = !send_touch_events_async_;
+      pending_async_touchmove_->event.dispatchType =
+          send_touch_events_async_ ? WebInputEvent::EventNonBlocking
+                                   : WebInputEvent::Blocking;
       touch = *pending_async_touchmove_;
       pending_async_touchmove_.reset();
     } else {
@@ -647,7 +650,7 @@ void TouchEventQueue::ForwardNextEventToRenderer() {
   // platform scrolling and JS pinching. Touchend events, however, remain
   // uncancelable, mitigating the risk of jank when transitioning to a fling.
   if (send_touch_events_async_ && touch.event.type != WebInputEvent::TouchStart)
-    touch.event.cancelable = false;
+    touch.event.dispatchType = WebInputEvent::EventNonBlocking;
 
   SendTouchEventImmediately(&touch);
 }
@@ -656,7 +659,7 @@ void TouchEventQueue::FlushPendingAsyncTouchmove() {
   DCHECK(!dispatching_touch_);
   std::unique_ptr<TouchEventWithLatencyInfo> touch =
       std::move(pending_async_touchmove_);
-  touch->event.cancelable = false;
+  touch->event.dispatchType = WebInputEvent::EventNonBlocking;
   touch_queue_.push_front(new CoalescedWebTouchEvent(*touch, true));
   SendTouchEventImmediately(touch.get());
 }
@@ -825,7 +828,7 @@ void TouchEventQueue::SendTouchEventImmediately(
   // timeout should not be started and the count also should not be increased.
   if (dispatching_touch_) {
     if (touch->event.type == WebInputEvent::TouchMove &&
-        !touch->event.cancelable) {
+        touch->event.dispatchType != WebInputEvent::Blocking) {
       // When we send out a uncancelable touch move, we increase the count and
       // we do not process input event ack any more, we will just ack to client
       // and wait for the ack from render. Also we will remove it from the front