Remove fields that are unused and reference classes that do not exist.

chrome/browser/cocoa/throbber_view.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.
 
 #import "chrome/browser/cocoa/throbber_view.h"
 
 #include <set>
 
 #include "base/logging.h"
 
@@ skipping 335 matching lines @@
   [self maintainTimer];
   [super viewDidHide];
 }
 
 // A visible ThrobberView may need to start animating.
 - (void)viewDidUnhide {
   [self maintainTimer];
   [super viewDidUnhide];
 }
 
-// Called when the ThrobberTimerTarget gets tickled by our timer. Advance the
-// frame, dirty the display, and kill the timer when it's no longer needed.
+// Called when the timer fires. Advance the frame, dirty the display, and remove
+// the throbber if it's no longer needed.
 - (void)animate {
   [dataDelegate_ advanceFrame];
   [self setNeedsDisplay:YES];
 
   if ([dataDelegate_ animationIsComplete]) {
     [[ThrobberTimer sharedThrobberTimer] removeThrobber:self];
   }
 }
 
 // Overridden to draw the appropriate frame in the image strip.
 - (void)drawRect:(NSRect)rect {
   [dataDelegate_ drawFrameInRect:[self bounds]];
 }
 
 @end