Deprecate use of user gestures during scroll-related touch events

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>
 
@@ skipping 65 matching lines @@
       client_(client),
       ack_handler_(ack_handler),
       routing_id_(routing_id),
       frame_tree_node_id_(-1),
       select_message_pending_(false),
       move_caret_pending_(false),
       mouse_move_pending_(false),
       current_ack_source_(ACK_SOURCE_NONE),
       flush_requested_(false),
       active_renderer_fling_count_(0),
+      touch_scroll_started_sent_(false),
       wheel_event_queue_(this,
                          UseGestureBasedWheelScrolling(),
                          kDefaultWheelScrollTransactionMs),
       touch_event_queue_(this, config.touch_config),
       gesture_event_queue_(this, this, config.gesture_config),
       device_scale_factor_(1.f) {
   DCHECK(sender);
   DCHECK(client);
   DCHECK(ack_handler);
   UpdateTouchAckTimeoutEnabled();
@@ skipping 58 matching lines @@
   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.type == blink::WebInputEvent::GestureScrollBegin)
+    if (gesture_event.event.type == blink::WebInputEvent::GestureScrollBegin) {
+      touch_scroll_started_sent_ = false;
+    } else if(!touch_scroll_started_sent_
+        && gesture_event.event.type ==
+            blink::WebInputEvent::GestureScrollUpdate) {
+      // A touch scroll hasn't really started until the first
+      // GestureScrollUpdate event.  Eg. if the page consumes all touchmoves
+      // then no scrolling really ever occurs (even though we still send
+      // GestureScrollBegin).
       touch_event_queue_.PrependTouchScrollNotification();
+      touch_scroll_started_sent_ = true;
+    }
     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 463 matching lines @@
 
   flush_requested_ = false;
   client_->DidFlush();
 }
 
 void InputRouterImpl::SetFrameTreeNodeId(int frameTreeNodeId) {
   frame_tree_node_id_ = frameTreeNodeId;
 }
 
 }  // namespace content