Notify Blink about start of gesture scroll through a queued event.

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 140 matching lines @@
     const GestureEventWithLatencyInfo& original_gesture_event) {
   input_stream_validator_.Validate(original_gesture_event.event);
 
   GestureEventWithLatencyInfo gesture_event(original_gesture_event);
 
   if (touch_action_filter_.FilterGestureEvent(&gesture_event.event))
     return;
 
   wheel_event_queue_.OnGestureScrollEvent(gesture_event);
 
-  if (gesture_event.event.sourceDevice == blink::WebGestureDeviceTouchscreen)
+  if (gesture_event.event.sourceDevice == blink::WebGestureDeviceTouchscreen) {
+    if (gesture_event.event.type == blink::WebInputEvent::GestureScrollBegin)
+      touch_event_queue_.PrependTouchScrollNotification();
     touch_event_queue_.OnGestureScrollEvent(gesture_event);
+  }
 
   gesture_event_queue_.QueueEvent(gesture_event);
 }
 
 void InputRouterImpl::SendTouchEvent(
     const TouchEventWithLatencyInfo& touch_event) {
   input_stream_validator_.Validate(touch_event.event);
   touch_event_queue_.QueueEvent(touch_event);
 }
 
@@ skipping 185 matching lines @@
 }
 
 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.
+  // cancelable (respect ACK disposition) or not, except touchmove and
+  // touchscollstarted.
   bool should_block = WebInputEventTraits::ShouldBlockEventStream(input_event);
+  if (WebInputEvent::isTouchEventType(input_event.type) &&
+      input_event.type != WebInputEvent::TouchMove &&
+      input_event.type != WebInputEvent::TouchScrollStarted) {
+    const WebTouchEvent& touch = static_cast<const WebTouchEvent&>(input_event);
+    DCHECK_EQ(should_block, touch.cancelable);
+  }
 
   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);
-  }
-
   // Generate a synthetic ack if the event was sent so it doesn't block.
   if (!should_block) {
     ProcessInputEventAck(
         input_event.type, INPUT_EVENT_ACK_STATE_IGNORED, latency_info,
         WebInputEventTraits::GetUniqueTouchEventId(input_event),
         IGNORING_DISPOSITION);
   }
 }
 
 bool InputRouterImpl::OfferToClient(const WebInputEvent& input_event,
@@ skipping 246 matching lines @@
 
   flush_requested_ = false;
   client_->DidFlush();
 }
 
 void InputRouterImpl::SetFrameTreeNodeId(int frameTreeNodeId) {
   frame_tree_node_id_ = frameTreeNodeId;
 }
 
 }  // namespace content