ObserverList::HasObserver now takes a const pointer.

ui/compositor/compositor.cc

 // Copyright (c) 2012 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 "ui/compositor/compositor.h"
 
 #include <algorithm>
 #include <deque>
 
 #include "base/bind.h"
@@ skipping 294 matching lines @@
 #if defined(OS_MACOSX)
   // Debugging instrumentation for crbug.com/401630.
   // TODO(ccameron): remove this.
   if (observer_list_.HasObserver(observer))
     observer->observing_count_ -= 1;
 #endif
 
   observer_list_.RemoveObserver(observer);
 }
 
-bool Compositor::HasObserver(CompositorObserver* observer) {
+bool Compositor::HasObserver(const CompositorObserver* observer) const {
   return observer_list_.HasObserver(observer);
 }
 
 void Compositor::AddAnimationObserver(CompositorAnimationObserver* observer) {
   animation_observer_list_.AddObserver(observer);
   host_->SetNeedsAnimate();
 }
 
 void Compositor::RemoveAnimationObserver(
     CompositorAnimationObserver* observer) {
   animation_observer_list_.RemoveObserver(observer);
 }
 
-bool Compositor::HasAnimationObserver(CompositorAnimationObserver* observer) {
+bool Compositor::HasAnimationObserver(
+    const CompositorAnimationObserver* observer) const {
   return animation_observer_list_.HasObserver(observer);
 }
 
 void Compositor::BeginMainFrame(const cc::BeginFrameArgs& args) {
   FOR_EACH_OBSERVER(CompositorAnimationObserver,
                     animation_observer_list_,
                     OnAnimationStep(args.frame_time));
   if (animation_observer_list_.might_have_observers())
     host_->SetNeedsAnimate();
 }
@@ skipping 110 matching lines @@
     // Call ScheduleDraw() instead of Draw() in order to allow other
     // CompositorObservers to be notified before starting another
     // draw cycle.
     ScheduleDraw();
   }
   FOR_EACH_OBSERVER(
       CompositorObserver, observer_list_, OnCompositingEnded(this));
 }
 
 }  // namespace ui