Consuming a touch move prevents only the next scroll update.

content/browser/renderer_host/input/gesture_event_packet.cc

Index: content/browser/renderer_host/input/gesture_event_packet.cc
diff --git a/content/browser/renderer_host/input/gesture_event_packet.cc b/content/browser/renderer_host/input/gesture_event_packet.cc
index d0fe17219b9e2ecba7b69d2ed15c5dece4ffba50..cef1d1b607d578a42097507b49c19d9d655e3d08 100644
--- a/content/browser/renderer_host/input/gesture_event_packet.cc
+++ b/content/browser/renderer_host/input/gesture_event_packet.cc
@@ -14,22 +14,33 @@ 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