Ignore button mouse enter for new tab button

chrome/browser/ui/cocoa/new_tab_button.mm

 // Copyright (c) 2010 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.
 
 #import "chrome/browser/ui/cocoa/new_tab_button.h"
 #import "chrome/browser/ui/cocoa/image_button_cell.h"
 
+// A simple override of the ImageButtonCell to disable handling of
+// -mouseEntered.
+@interface NewTabButtonCell : ImageButtonCell
+
+- (void)mouseEntered:(NSEvent*)theEvent;
+
+@end
+
+@implementation NewTabButtonCell
+
+- (void)mouseEntered:(NSEvent*)theEvent {
+  // Ignore this since the NTB enter is handled by the TabStripController.
+}
+
+@end
+
+
 @implementation NewTabButton
 
 + (Class)cellClass {
-  return [ImageButtonCell class];
+  return [NewTabButtonCell class];
 }
 
 // Approximate the shape. It doesn't need to be perfect. This will need to be
 // updated if the size or shape of the icon ever changes.
 // TODO(pinkerton): use a click mask image instead of hard-coding points.
 - (NSBezierPath*)pathForButton {
   if (imagePath_.get())
     return imagePath_.get();
 
   // Cache the path as it doesn't change (the coordinates are local to this
@@ skipping 16 matching lines @@
 
 // Override to only accept clicks within the bounds of the defined path, not
 // the entire bounding box. |aPoint| is in the superview's coordinate system.
 - (NSView*)hitTest:(NSPoint)aPoint {
   if ([self pointIsOverButton:aPoint])
     return [super hitTest:aPoint];
   return nil;
 }
 
 @end