Add a dead zone when dragging tabs horizontally on Mac

chrome/browser/ui/cocoa/tabs/tab_strip_drag_controller.h

 // Copyright (c) 2011 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 CHROME_BROWSER_UI_COCOA_TABS_TAB_STRIP_DRAG_CONTROLLER_H_
 #define CHROME_BROWSER_UI_COCOA_TABS_TAB_STRIP_DRAG_CONTROLLER_H_
 
 #import <Cocoa/Cocoa.h>
 #include <map>
 
@@ skipping 17 matching lines @@
 
 // This controller is owned by the TabStripController and is used to delegate
 // all the logic for tab dragging from the TabView's events.
 @interface TabStripDragController : NSObject<TabDraggingEventTarget> {
  @private
   TabStripController* tabStrip_;  // Weak; owns this.
 
   // These are released on mouseUp:
   BOOL moveWindowOnDrag_;  // Set if the only tab of a window is dragged.
   BOOL tabWasDragged_;  // Has the tab been dragged?
+  BOOL outOfTabHorizontalDeadZone_; // Moved out of its horizontal dead zone?
   BOOL draggingWithinTabStrip_;  // Did drag stay in the current tab strip?
   BOOL chromeIsVisible_;
 
   NSTimeInterval tearTime_;  // Time since tear happened
   NSPoint tearOrigin_;  // Origin of the tear rect
   NSPoint dragOrigin_;  // Origin point of the drag
 
   TabWindowController* sourceController_;  // weak. controller starting the drag
   NSWindow* sourceWindow_;  // Weak. The window starting the drag.
   NSRect sourceWindowFrame_;
@@ skipping 14 matching lines @@
 @property(readonly) TabController* draggedTab;
 
 // Designated initializer.
 - (id)initWithTabStripController:(TabStripController*)controller;
 
 // TabDraggingEventTarget methods are also implemented.
 
 @end
 
 #endif  // CHROME_BROWSER_UI_COCOA_TABS_TAB_STRIP_DRAG_CONTROLLER_H_