Update ui::CompositorObserver instrumentation

ui/compositor/compositor.cc

Index: ui/compositor/compositor.cc
diff --git a/ui/compositor/compositor.cc b/ui/compositor/compositor.cc
index 14b5366b0b536d2a87ef39228c56b1a75def16e1..a33768cbec981185cd3f4849d1a1b68ba2121e02 100644
--- a/ui/compositor/compositor.cc
+++ b/ui/compositor/compositor.cc
@@ -278,9 +278,7 @@ scoped_refptr<CompositorVSyncManager> Compositor::vsync_manager() const {
 }
 
 void Compositor::AddObserver(CompositorObserver* observer) {
-#if defined(OS_MACOSX)
-  // Debugging instrumentation for crbug.com/401630.
-  // TODO(ccameron): remove this.
+#if DCHECK_IS_ON
   CHECK(observer);

[danakj, 2014/08/12 20:57:54]

DCHECK?

[ccameron, 2014/08/12 21:04:24]

Done.

   if (!observer_list_.HasObserver(observer))
     observer->observing_count_ += 1;
@@ -290,9 +288,7 @@ void Compositor::AddObserver(CompositorObserver* observer) {
 }
 
 void Compositor::RemoveObserver(CompositorObserver* observer) {
-#if defined(OS_MACOSX)
-  // Debugging instrumentation for crbug.com/401630.
-  // TODO(ccameron): remove this.
+#if DCHECK_IS_ON
   if (observer_list_.HasObserver(observer))
     observer->observing_count_ -= 1;
 #endif