Remove --ash-enable-tray-dragging flag

ash/shelf/shelf_layout_manager.h

 // Copyright 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 ASH_SHELF_SHELF_LAYOUT_MANAGER_H_
 #define ASH_SHELF_SHELF_LAYOUT_MANAGER_H_
 
 #include <vector>
 
 #include "ash/ash_export.h"
@@ skipping 135 matching lines @@
   // the shelf renders slightly differently.
   void SetWindowOverlapsShelf(bool value);
   bool window_overlaps_shelf() const { return window_overlaps_shelf_; }
 
   void AddObserver(ShelfLayoutManagerObserver* observer);
   void RemoveObserver(ShelfLayoutManagerObserver* observer);
 
   // Gesture related functions:
   void OnGestureEdgeSwipe(const ui::GestureEvent& gesture);
   void StartGestureDrag(const ui::GestureEvent& gesture);
-  enum DragState {
-    DRAG_SHELF,
-    DRAG_TRAY
-  };
-  // Returns DRAG_SHELF if the gesture should continue to drag the entire shelf.
-  // Returns DRAG_TRAY if the gesture can start dragging the tray-bubble from
-  // this point on.
-  DragState UpdateGestureDrag(const ui::GestureEvent& gesture);
+  void UpdateGestureDrag(const ui::GestureEvent& gesture);
   void CompleteGestureDrag(const ui::GestureEvent& gesture);
   void CancelGestureDrag();
 
   // Set an animation duration override for the show / hide animation of the
   // shelf. Specifying 0 leads to use the default.
   void SetAnimationDurationOverride(int duration_override_in_ms);
 
   // Overridden from SnapLayoutManager:
   void OnWindowResized() override;
   void SetChildBounds(aura::Window* child,
@@ skipping 229 matching lines @@
 
   // The show hide animation duration override or 0 for default.
   int duration_override_in_ms_;
 
   DISALLOW_COPY_AND_ASSIGN(ShelfLayoutManager);
 };
 
 }  // namespace ash
 
 #endif  // ASH_SHELF_SHELF_LAYOUT_MANAGER_H_