[Mac] Make ExtensionInstalledBubbleController is-a BaseBubbleController.

chrome/browser/ui/cocoa/base_bubble_controller.h

 // 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 <Cocoa/Cocoa.h>
 
 #import "base/mac/cocoa_protocols.h"
 #include "base/memory/scoped_ptr.h"
 
 namespace BaseBubbleControllerInternal {
@@ skipping 16 matching lines @@
 @interface BaseBubbleController : NSWindowController<NSWindowDelegate> {
  @private
   NSWindow* parentWindow_;  // weak
   NSPoint anchor_;
   IBOutlet InfoBubbleView* bubble_;  // to set arrow position
   // Bridge that listens for notifications.
   scoped_ptr<BaseBubbleControllerInternal::Bridge> base_bridge_;
 }
 
 @property(nonatomic, readonly) NSWindow* parentWindow;
+// The point in base screen coordinates at which the bubble should open and the
+// arrow tip points.
 @property(nonatomic, assign) NSPoint anchorPoint;
 @property(nonatomic, readonly) InfoBubbleView* bubble;
 
 // Creates a bubble. |nibPath| is just the basename, e.g. @"FirstRunBubble".
 // |anchoredAt| is in screen space. You need to call -showWindow: to make the
 // bubble visible. It will autorelease itself when the user dismisses the
 // bubble.
 // This is the designated initializer.
 - (id)initWithWindowNibPath:(NSString*)nibPath
                parentWindow:(NSWindow*)parentWindow
@@ skipping 15 matching lines @@
 // contentView with an instance of InfoBubbleView.
 - (id)initWithWindow:(NSWindow*)theWindow
         parentWindow:(NSWindow*)parentWindow
           anchoredAt:(NSPoint)anchoredAt;
 
 // Creates an autoreleased separator view with a given frame. The height of the
 // frame is ignored.
 - (NSBox*)separatorWithFrame:(NSRect)frame;
 
 @end