Display a tooltip when mousing over a tab title.

chrome/browser/cocoa/tab_controller.mm

 // Copyright (c) 2009 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.
 
 #include "base/mac_util.h"
 #import "chrome/browser/cocoa/tab_controller.h"
 #import "chrome/browser/cocoa/tab_controller_target.h"
 
 @implementation TabController
 
@@ skipping 38 matching lines @@
   [self internalSetSelected:selected_];
 }
 
 - (IBAction)closeTab:(id)sender {
   if ([[self target] respondsToSelector:@selector(closeTab:)]) {
     [[self target] performSelector:@selector(closeTab:)
                         withObject:[self view]];
   }
 }
 
+- (void)setTitle:(NSString *)title {
+  [backgroundButton_ setToolTip:title];
+  [super setTitle:title];
+}
+
 - (void)setSelected:(BOOL)selected {
   if (selected_ != selected)
     [self internalSetSelected:selected];
 }
 
 - (BOOL)selected {
   return selected_;
 }
 
 - (void)setIconView:(NSView*)iconView {
   NSRect currentFrame = [iconView_ frame];
   [iconView_ removeFromSuperview];
   iconView_ = iconView;
   [iconView_ setFrame:currentFrame];
   [[self view] addSubview:iconView_];
 }
 
 - (NSView*)iconView {
   return iconView_;
 }
 
+- (NSString *)toolTip {
+  return [backgroundButton_ toolTip];
+}
+
 @end