[Mac][Material Design] Fix TabStripController test that fails under MD.

chrome/browser/ui/cocoa/tabs/tab_strip_controller.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 CHROME_BROWSER_UI_COCOA_TABS_TAB_STRIP_CONTROLLER_H_
 #define CHROME_BROWSER_UI_COCOA_TABS_TAB_STRIP_CONTROLLER_H_
 
 #import <Cocoa/Cocoa.h>
 
 #include <memory>
@@ skipping 246 matching lines @@
 // Returns YES if the user is allowed to drag tabs on the strip at this moment.
 // For example, this returns NO if there are any pending tab close animtations.
 - (BOOL)tabDraggingAllowed;
 
 // Default height for tabs.
 + (CGFloat)defaultTabHeight;
 
 // Default indentation for tabs (see |leftIndentForControls_|).
 + (CGFloat)defaultLeftIndentForControls;
 
+// Returns the amount by which tabs overlap.
++ (CGFloat)tabOverlap;
+
 // Returns the currently active TabContentsController.
 - (TabContentsController*)activeTabContentsController;
 
 // Adds custom traffic light buttons to the tab strip. Idempotent.
 - (void)addCustomWindowControls;
 
 // Removes custom traffic light buttons from the tab strip. Idempotent.
 - (void)removeCustomWindowControls;
 
 // Gets the tab and the alert state to check whether the window
@@ skipping 11 matching lines @@
 - (TabAlertState)alertStateForContents:(content::WebContents*)contents;
 
 @end
 
 @interface TabStripController(TestingAPI)
 - (void)setTabTitle:(TabController*)tab
        withContents:(content::WebContents*)contents;
 @end
 
 #endif  // CHROME_BROWSER_UI_COCOA_TABS_TAB_STRIP_CONTROLLER_H_