Use Titlebar instead of TitleBar consistently in panels code.

chrome/browser/ui/panels/panel_titlebar_view_cocoa.h

Index: chrome/browser/ui/panels/panel_titlebar_view_cocoa.h
diff --git a/chrome/browser/ui/panels/panel_titlebar_view_cocoa.h b/chrome/browser/ui/panels/panel_titlebar_view_cocoa.h
index c8abf6f8372c5473c3ab7d95377303b0f1109504..a074475fa5471a1b2466b2b5682d85bf635109c9 100644
--- a/chrome/browser/ui/panels/panel_titlebar_view_cocoa.h
+++ b/chrome/browser/ui/panels/panel_titlebar_view_cocoa.h
@@ -12,8 +12,8 @@
 @class CrTrackingArea;
 @class PanelWindowControllerCocoa;
 
-// A class that works as a custom title bar for Panels. It is placed on top of
-// the regular Cocoa title bar. We paint theme image on it, and it's
+// A class that works as a custom titlebar for Panels. It is placed on top of
+// the regular Cocoa titlebar. We paint theme image on it, and it's
 // the place for the close button, wrench button, page favicon, title label.
 // It also facilitates dragging and minimization of the panels, and changes
 // color as 'new activity' indicator.
@@ -35,7 +35,7 @@
   // Attaches this view to the controller_'s window as a titlebar.
 - (void)attach;
 
-  // Should be called when size of the title bar changes.
+  // Should be called when size of the titlebar changes.
 - (void)updateCloseButtonLayout;
 
   // Accessor to Panel's controller.