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;
-  if (!event.touchesLength)
-    return false;
-  for (size_t i = 0; i < event.touchesLength; i++) {
-    if (event.touches[i].state != WebTouchPoint::StatePressed)
-      return false;
-  }
-  return true;
-}
-
 GestureEventPacket::GestureSource
 ToGestureSource(const WebTouchEvent& event) {
-  return IsTouchSequenceStart(event) ? GestureEventPacket::TOUCH_BEGIN
-                                     : GestureEventPacket::TOUCH;
+  switch(event.type) {
+    case WebInputEvent::TouchStart:
+      if (!event.touchesLength)
+        return GestureEventPacket::OUT_OF_ORDER;

[jdduke (slow), 2014/02/13 19:40:00]

I'm not sure about the OUT_OF_ORDER source... the packet isn't really
determining that, it's simply determining if we have a valid touch... What if we
instead rename INVALID to UNDEFINED, and rename OUT_OF_ORDER to INVALID?

Also, I guess you might as well move the "if (!event.touchesLength)" check to
the beginning of the function.

[tdresser, 2014/02/13 20:34:31]

Done.

+      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:
+      if (!event.touchesLength)
+        return GestureEventPacket::OUT_OF_ORDER;
+      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::OUT_OF_ORDER;
+  }
 }
 
 }  // namespace
 
 GestureEventPacket::GestureEventPacket()
     : gesture_count_(0),
       gesture_source_(INVALID) {}
 
 GestureEventPacket::GestureEventPacket(GestureSource source)
     : gesture_count_(0),
@@ skipping 13 matching lines @@
 }
 
 GestureEventPacket GestureEventPacket::FromTouchTimeout(
     const WebGestureEvent& event) {
   GestureEventPacket packet(TOUCH_TIMEOUT);
   packet.Push(event);
   return packet;
 }
 
 }  // namespace content