Use Titlebar instead of TitleBar consistently in panels code.

chrome/browser/ui/panels/panel_titlebar_view_cocoa.mm

 // 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.
 
 #import "chrome/browser/ui/panels/panel_titlebar_view_cocoa.h"
 
 #import <Cocoa/Cocoa.h>
 
 #include "base/logging.h"
 #import "chrome/browser/ui/cocoa/tracking_area.h"
@@ skipping 59 matching lines @@
   // contentView  titlebar
   NSRect rootViewBounds = [[self superview] bounds];
   NSRect contentFrame = [[[controller_ window] contentView] frame];
   NSRect titlebarFrame =
       NSMakeRect(NSMinX(contentFrame),
                  NSMaxY(contentFrame),
                  NSWidth(contentFrame),
                  NSMaxY(rootViewBounds) - NSMaxY(contentFrame));
   [self setFrame:titlebarFrame];
 
-  // Update layout of controls in the title bar.
+  // Update layout of controls in the titlebar.
   [self updateCloseButtonLayout];
 
   // Set autoresizing behavior: glued to edges on left, top and right.
   [self setAutoresizingMask:(NSViewMinYMargin | NSViewWidthSizable)];
 }
 
 - (void)updateCloseButtonLayout {
   NSRect buttonBounds = [closeButton_ bounds];
   NSRect bounds = [self bounds];
 
@@ skipping 34 matching lines @@
   return controller_;
 }
 
 // (Private/TestingAPI)
 - (void)simulateCloseButtonClick {
   [[closeButton_ cell] performClick:closeButton_];
 }
 
 @end