Ignore button mouse enter for new tab button

chrome/browser/ui/cocoa/new_tab_button.mm

Index: chrome/browser/ui/cocoa/new_tab_button.mm
diff --git a/chrome/browser/ui/cocoa/new_tab_button.mm b/chrome/browser/ui/cocoa/new_tab_button.mm
index ad719b803fb763a9211fbd210b79b5f4c8d41238..d6411f8901a0c9f27cb8699b16dfebc09093d49b 100644
--- a/chrome/browser/ui/cocoa/new_tab_button.mm
+++ b/chrome/browser/ui/cocoa/new_tab_button.mm
@@ -5,10 +5,27 @@
 #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