Allow partial update for notification update API

chrome/browser/ui/cocoa/notifications/balloon_controller_unittest.mm

Index: chrome/browser/ui/cocoa/notifications/balloon_controller_unittest.mm
diff --git a/chrome/browser/ui/cocoa/notifications/balloon_controller_unittest.mm b/chrome/browser/ui/cocoa/notifications/balloon_controller_unittest.mm
index 58c279f0aea9f78b06cfc79f0611bf4eae6f4bbc..b8f813732595925b845ba3c7fc348f8958fd2c24 100644
--- a/chrome/browser/ui/cocoa/notifications/balloon_controller_unittest.mm
+++ b/chrome/browser/ui/cocoa/notifications/balloon_controller_unittest.mm
@@ -31,7 +31,9 @@ namespace {
 class MockBalloonCollection : public BalloonCollection {
   virtual void Add(const Notification& notification,
                    Profile* profile) OVERRIDE {}
-  virtual bool DoesIdExist(const std::string& id) OVERRIDE { return false; }
+  virtual const Notification* FindById(const std::string& id) const OVERRIDE {
+    return NULL;
+  }
   virtual bool RemoveById(const std::string& id) OVERRIDE { return false; }
   virtual bool RemoveBySourceOrigin(const GURL& origin) OVERRIDE {
     return false;