Allow ui::Compositor to disable commits during tab-switch

cc/trees/proxy.h

Index: cc/trees/proxy.h
diff --git a/cc/trees/proxy.h b/cc/trees/proxy.h
index 0d6d3e9a87cccc9f09ccc16fa9dbb06dbb8c037f..945e54792cafb7e5eefd8959e229cc8cb0be751b 100644
--- a/cc/trees/proxy.h
+++ b/cc/trees/proxy.h
@@ -80,9 +80,8 @@ class CC_EXPORT Proxy {
 
   virtual void NotifyInputThrottledUntilCommit() = 0;
 
-  // Defers commits until it is reset. It is only supported when in threaded
-  // mode. It's an error to make a sync call like CompositeAndReadback while
-  // commits are deferred.
+  // Defers commits until it is reset. It is only supported when using a
+  // scheduler.
   virtual void SetDeferCommits(bool defer_commits) = 0;
 
   virtual void MainThreadHasStoppedFlinging() = 0;