Adopt "QuickScale" double-tap drag zoom code in the GestureProvider

ui/events/gesture_detection/gesture_provider.h

 // 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.
 
 #ifndef UI_EVENTS_GESTURE_DETECTION_GESTURE_PROVIDER_H_
 #define UI_EVENTS_GESTURE_DETECTION_GESTURE_PROVIDER_H_
 
 #include "base/basictypes.h"
 #include "base/memory/scoped_ptr.h"
 #include "ui/events/gesture_detection/gesture_detection_export.h"
@@ skipping 48 matching lines @@
   // detection allows for rapid and responsive single-tap gestures.
   void SetDoubleTapSupportForPageEnabled(bool enabled);
 
   // Whether a scroll gesture is in-progress.
   bool IsScrollInProgress() const;
 
   // Whether a pinch gesture is in-progress (i.e. a pinch update has been
   // forwarded and detection is still active).
   bool IsPinchInProgress() const;
 
-  // Whether a double tap-gesture is in-progress.
+  // Whether a double-tap gesture is in-progress (either double-tap or
+  // double-tap drag zoom).
   bool IsDoubleTapInProgress() const;
 
+  // Whether double-tap gesture detection is supported.
+  bool IsDoubleTapSupportedEnabled() const;

[tdresser, 2014/04/03 17:53:30]

SupportedEnabled -> Supported|Enabled.

[jdduke (slow), 2014/04/03 19:28:01]

Done.

+
   // Whether the tap gesture delay is explicitly disabled (independent of
   // whether double-tap is supported), see |Config.disable_click_delay|.
   bool IsClickDelayDisabled() const;
 
   // May be NULL if there is no currently active touch sequence.
   const ui::MotionEvent* current_down_event() const {
     return current_down_event_.get();
   }
 
  private:
   void InitGestureDetectors(const Config& config);
 
   bool CanHandle(const MotionEvent& event) const;
 
   void Fling(base::TimeTicks time,
              float x,
              float y,
              float velocity_x,
              float velocity_y);
   void Send(const GestureEventData& gesture);
   void SendTapCancelIfNecessary(const MotionEvent& event);
   bool SendLongTapIfNecessary(const MotionEvent& event);
   void EndTouchScrollIfNecessary(base::TimeTicks time,
                                  bool send_scroll_end_event);
+  void UpdateDoubleTapDetectionSupport();
 
   GestureProviderClient* const client_;
 
   class GestureListenerImpl;
   friend class GestureListenerImpl;
   scoped_ptr<GestureListenerImpl> gesture_listener_;
 
   class ScaleGestureListenerImpl;
   friend class ScaleGestureListenerImpl;
   scoped_ptr<ScaleGestureListenerImpl> scale_gesture_listener_;
 
   scoped_ptr<MotionEvent> current_down_event_;
 
   // Whether a GESTURE_SHOW_PRESS was sent for the current touch sequence.
   // Sending a GESTURE_TAP event will forward a GESTURE_SHOW_PRESS if one has
   // not yet been sent.
   bool needs_show_press_event_;
 
   // Whether a sent GESTURE_TAP_DOWN event has yet to be accompanied by a
   // corresponding GESTURE_TAP, GESTURE_TAP_CANCEL or GESTURE_DOUBLE_TAP.
   bool needs_tap_ending_event_;
 
   // Whether the respective {SCROLL,PINCH}_BEGIN gestures have been terminated
   // with a {SCROLL,PINCH}_END.
   bool touch_scroll_in_progress_;
   bool pinch_in_progress_;
 
+  // Whether double-tap gesture detection is currently supported.
+  bool double_tap_support_for_page_;
+  bool double_tap_support_for_platform_;
+
   // Keeps track of the current GESTURE_LONG_PRESS event. If a context menu is
   // opened after a GESTURE_LONG_PRESS, this is used to insert a
   // GESTURE_TAP_CANCEL for removing any ::active styling.
   base::TimeTicks current_longpress_time_;
 };
 
 }  //  namespace ui
 
 #endif  // UI_EVENTS_GESTURE_DETECTION_GESTURE_PROVIDER_H_