Don't treat first touch move differently from future touch moves

content/browser/renderer_host/input/touch_event_queue.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/touch_event_queue.h"
 
 #include "base/auto_reset.h"
 #include "base/debug/trace_event.h"
 #include "base/stl_util.h"
 #include "content/browser/renderer_host/input/timeout_monitor.h"
@@ skipping 331 matching lines @@
       touch_filtering_state_(TOUCH_FILTERING_STATE_DEFAULT),
       ack_timeout_enabled_(config.touch_ack_timeout_supported),
       touchmove_slop_suppressor_(new TouchMoveSlopSuppressor(
           config.touchmove_slop_suppression_length_dips +
           (config.touchmove_slop_suppression_region_includes_boundary
                ? kSlopEpsilon
                : -kSlopEpsilon))),
       send_touch_events_async_(false),
       needs_async_touchmove_for_outer_slop_region_(false),
       last_sent_touch_timestamp_sec_(0),
-      touch_scrolling_mode_(config.touch_scrolling_mode) {
+  touch_scrolling_mode_(config.touch_scrolling_mode),
+  seen_scroll_update_this_sequence_(false) {
   DCHECK(client);
   if (ack_timeout_enabled_) {
     timeout_handler_.reset(
         new TouchTimeoutHandler(this, config.touch_ack_timeout_delay));
   }
 }
 
 TouchEventQueue::~TouchEventQueue() {
   if (!touch_queue_.empty())
     STLDeleteElements(&touch_queue_);
@@ skipping 164 matching lines @@
   if (dispatching_touch_ &&
       touch_filtering_state_ == FORWARD_TOUCHES_UNTIL_TIMEOUT &&
       ShouldTouchTriggerTimeout(touch.event)) {
     DCHECK(timeout_handler_);
     timeout_handler_->Start(touch);
   }
 }
 
 void TouchEventQueue::OnGestureScrollEvent(
     const GestureEventWithLatencyInfo& gesture_event) {
-  if (gesture_event.event.type != blink::WebInputEvent::GestureScrollBegin)
-    return;
+  if (gesture_event.event.type == blink::WebInputEvent::GestureScrollBegin) {
+    seen_scroll_update_this_sequence_ = false;
 
-  if (touch_filtering_state_ != DROP_ALL_TOUCHES &&
-      touch_filtering_state_ != DROP_TOUCHES_IN_SEQUENCE) {
-    DCHECK(!touchmove_slop_suppressor_->suppressing_touchmoves())
-        << "The renderer should be offered a touchmove before scrolling begins";
-  }
-
-  if (touch_scrolling_mode_ == TOUCH_SCROLLING_MODE_ASYNC_TOUCHMOVE) {
     if (touch_filtering_state_ != DROP_ALL_TOUCHES &&
         touch_filtering_state_ != DROP_TOUCHES_IN_SEQUENCE) {
+      DCHECK(!touchmove_slop_suppressor_->suppressing_touchmoves())
+          << "The renderer should be offered a touchmove before scrolling "
+             "begins";
+    }
+
+    if (touch_scrolling_mode_ == TOUCH_SCROLLING_MODE_ASYNC_TOUCHMOVE &&
+        touch_filtering_state_ != DROP_ALL_TOUCHES &&
+        touch_filtering_state_ != DROP_TOUCHES_IN_SEQUENCE &&
+        (touch_ack_states_.empty() ||
+         AllTouchAckStatesHaveState(
+             INPUT_EVENT_ACK_STATE_NO_CONSUMER_EXISTS))) {
       // If no touch points have a consumer, prevent all subsequent touch events
       // received during the scroll from reaching the renderer. This ensures
       // that the first touchstart the renderer sees in any given sequence can
       // always be preventDefault'ed (cancelable == true).
       // TODO(jdduke): Revisit if touchstarts during scroll are made cancelable.
-      if (touch_ack_states_.empty() ||
-          AllTouchAckStatesHaveState(
-              INPUT_EVENT_ACK_STATE_NO_CONSUMER_EXISTS)) {
-        touch_filtering_state_ = DROP_TOUCHES_IN_SEQUENCE;
-        return;
-      }
+      touch_filtering_state_ = DROP_TOUCHES_IN_SEQUENCE;
     }
+    return;
+  }
 
+  if (gesture_event.event.type != blink::WebInputEvent::GestureScrollUpdate ||
+      seen_scroll_update_this_sequence_)
+    return;
+
+  if (touch_scrolling_mode_ == TOUCH_SCROLLING_MODE_ASYNC_TOUCHMOVE) {
     pending_async_touchmove_.reset();
     send_touch_events_async_ = true;
     needs_async_touchmove_for_outer_slop_region_ = true;
     return;
   }
 
   if (touch_scrolling_mode_ != TOUCH_SCROLLING_MODE_TOUCHCANCEL)
     return;
 
   // We assume that scroll events are generated synchronously from
@@ skipping 241 matching lines @@
        iter != end;
        ++iter) {
     if (iter->second != ack_state)
       return false;
   }
 
   return true;
 }
 
 }  // namespace content