Consuming a touch move prevents only the next scroll update.

content/browser/renderer_host/input/gesture_event_packet.cc

 // Copyright 2014 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/gesture_event_packet.h"
 
 #include "base/logging.h"
 
 using blink::WebGestureEvent;
 using blink::WebInputEvent;
 using blink::WebTouchEvent;
 using blink::WebTouchPoint;
 
 namespace content {
 namespace {
 
-bool IsTouchSequenceStart(const WebTouchEvent& event) {
-  if (event.type != WebInputEvent::TouchStart)
-    return false;
+GestureEventPacket::GestureSource ToGestureSource(const WebTouchEvent& event) {
   if (!event.touchesLength)
-    return false;
-  for (size_t i = 0; i < event.touchesLength; i++) {
-    if (event.touches[i].state != WebTouchPoint::StatePressed)
-      return false;
+    return GestureEventPacket::INVALID;
+  switch (event.type) {
+    case WebInputEvent::TouchStart:
+      for (size_t i = 0; i < event.touchesLength; i++) {
+        if (event.touches[i].state != WebTouchPoint::StatePressed)
+          return GestureEventPacket::TOUCH_BEGIN;
+      }
+      return GestureEventPacket::TOUCH_SEQUENCE_BEGIN;
+    case WebInputEvent::TouchMove:
+      return GestureEventPacket::TOUCH_MOVE;
+    case WebInputEvent::TouchEnd:
+    case WebInputEvent::TouchCancel:
+      for (size_t i = 0; i < event.touchesLength; i++) {
+        if (event.touches[i].state != WebTouchPoint::StateReleased &&
+            event.touches[i].state != WebTouchPoint::StateCancelled) {
+          return GestureEventPacket::TOUCH_END;
+        }
+      }
+      return GestureEventPacket::TOUCH_SEQUENCE_END;
+    default:
+      return GestureEventPacket::INVALID;
   }
-  return true;
-}
-
-GestureEventPacket::GestureSource
-ToGestureSource(const WebTouchEvent& event) {
-  return IsTouchSequenceStart(event) ? GestureEventPacket::TOUCH_BEGIN
-                                     : GestureEventPacket::TOUCH;
 }
 
 }  // namespace
 
 GestureEventPacket::GestureEventPacket()
     : gesture_count_(0),
-      gesture_source_(INVALID) {}
+      gesture_source_(UNDEFINED) {}
 
 GestureEventPacket::GestureEventPacket(GestureSource source)
     : gesture_count_(0),
       gesture_source_(source) {
-  DCHECK_NE(gesture_source_, INVALID);
+  DCHECK_NE(gesture_source_, UNDEFINED);
 }
 
 GestureEventPacket::~GestureEventPacket() {}
 
 void GestureEventPacket::Push(const blink::WebGestureEvent& gesture) {
   CHECK_LT(gesture_count_, static_cast<size_t>(kMaxGesturesPerTouch));
   gestures_[gesture_count_++] = gesture;
 }
 
 GestureEventPacket GestureEventPacket::FromTouch(const WebTouchEvent& event) {
   return GestureEventPacket(ToGestureSource(event));
 }
 
 GestureEventPacket GestureEventPacket::FromTouchTimeout(
     const WebGestureEvent& event) {
   GestureEventPacket packet(TOUCH_TIMEOUT);
   packet.Push(event);
   return packet;
 }
 
 }  // namespace content