Consuming any touch move before SCROLL_START prevents the scroll from occuring in Aura

ui/events/gestures/gesture_sequence.h

 // Copyright (c) 2012 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.
 
 #ifndef UI_EVENTS_GESTURES_GESTURE_SEQUENCE_H_
 #define UI_EVENTS_GESTURES_GESTURE_SEQUENCE_H_
 
 #include "base/timer/timer.h"
 #include "ui/events/event_constants.h"
 #include "ui/events/gestures/gesture_point.h"
 #include "ui/events/gestures/gesture_recognizer.h"
 #include "ui/gfx/rect.h"
 
 namespace ui {
 class TouchEvent;
 class GestureEvent;
 
 // Gesture state.
 enum GestureState {
   GS_NO_GESTURE,
   GS_PENDING_SYNTHETIC_CLICK,
+  // One finger is down: tap could occur, but scroll cannot

[sadrul, 2014/01/17 17:11:35]

Mention that scroll/pinch can happen if a second touch-point is pressed.

[tdresser, 2014/01/17 19:48:42]

Done.

   GS_PENDING_SYNTHETIC_CLICK_NO_SCROLL,
+  // One finger is down: no gestures can occur until the number of active touch
+  // points changes.
+  GS_SYNTHETIC_CLICK_ABORTED,
   GS_SCROLL,
   GS_PINCH,
   GS_PENDING_TWO_FINGER_TAP,
   GS_PENDING_TWO_FINGER_TAP_NO_PINCH,
   GS_PENDING_PINCH,
   GS_PENDING_PINCH_NO_PINCH,
 };
 
 enum ScrollType {
   ST_FREE,
@@ skipping 203 matching lines @@
   gfx::Point last_touch_location_;
 
   GestureSequenceDelegate* delegate_;
 
   DISALLOW_COPY_AND_ASSIGN(GestureSequence);
 };
 
 }  // namespace ui
 
 #endif  // UI_EVENTS_GESTURES_GESTURE_SEQUENCE_H_