Update the Notification Blink API to use integral persistent ids.

Source/modules/notifications/Notification.h

Index: Source/modules/notifications/Notification.h
diff --git a/Source/modules/notifications/Notification.h b/Source/modules/notifications/Notification.h
index 1f780a0a9bfdd265eb3e0c2c89bc3e0ed2ae1cb6..77a79313558bed5c1b68261eac10dfc7c3b5a79a 100644
--- a/Source/modules/notifications/Notification.h
+++ b/Source/modules/notifications/Notification.h
@@ -64,6 +64,8 @@ public:
     static Notification* create(ExecutionContext*, const String& title, const NotificationOptions&, ExceptionState&);
 
     // Used for embedder-created Notification objects. Will initialize the Notification's state as showing.
+    static Notification* create(ExecutionContext*, int64_t persistentId, const WebNotificationData&);
+    // TODO(peter): Remove this method when the embedder only passes us int64_t persistent notification ids.
     static Notification* create(ExecutionContext*, const String& persistentId, const WebNotificationData&);
 
     virtual ~Notification();
@@ -130,7 +132,8 @@ private:
     void setSilent(bool silent) { m_silent = silent; }
     void setSerializedData(PassRefPtr<SerializedScriptValue> data) { m_serializedData = data; }
 
-    void setPersistentId(const String& persistentId) { m_persistentId = persistentId; }
+    void setPersistentId(int64_t persistentId) { m_persistentId = persistentId; }
+    void setPersistentIdString(const String& persistentId) { m_persistentIdString = persistentId; }
 
 private:
     String m_title;
@@ -146,7 +149,8 @@ private:
     // Notifications can either be bound to the page, which means they're identified by
     // their delegate, or persistent, which means they're identified by a persistent Id
     // given to us by the embedder. This influences how we close the notification.
-    String m_persistentId;
+    int64_t m_persistentId;
+    String m_persistentIdString;
 
     enum NotificationState {
         NotificationStateIdle,