Stop refcounting SkDeferredCanvas::NotificationClient

User code (i.e. WebKit) is now responsible for the lifetime scope of the notification client.
With http://trac.webkit.org/changeset/125804 skia-side ref counting has become unnecessary and undesirable.
Review URL: https://codereview.appspot.com/6443146

git-svn-id: http://skia.googlecode.com/svn/trunk@5169 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/include/utils/SkDeferredCanvas.h b/include/utils/SkDeferredCanvas.h
index f531371..ff32351 100644
--- a/include/utils/SkDeferredCanvas.h
+++ b/include/utils/SkDeferredCanvas.h
@@ -48,8 +48,11 @@
     /**
      *  Specify a NotificationClient to be used by this canvas. Calling
      *  setNotificationClient will release the previously set 
-     *  NotificationClient, if any. Takes a reference on the notification
-     *  client.
+     *  NotificationClient, if any. SkDeferredCanvas does not take ownership
+     *  of the notification client.  Therefore user code is resposible
+     *  for its destruction.  The notification client must be unregistered
+     *  by calling setNotificationClient(NULL) if it is destroyed before
+     *  this canvas.
      *  Note: Must be called after the device is set with setDevice.
      *
      *  @param notificationClient interface for dispatching notifications
@@ -167,10 +170,8 @@
     virtual SkDrawFilter* setDrawFilter(SkDrawFilter* filter) SK_OVERRIDE;
 
 public:
-    class NotificationClient : public SkRefCnt {
+    class NotificationClient {
     public:
-        SK_DECLARE_INST_COUNT(NotificationClient)
-
         /**
          *  Called before executing one or several draw commands, which means
          *  once per flush when deferred rendering is enabled.