Add hooks for BeforeInstallPromptEvent to be redispatched.

Source/modules/app_banner/BeforeInstallPromptEvent.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef BeforeInstallPromptEvent_h
 #define BeforeInstallPromptEvent_h
 
 #include "bindings/core/v8/ScriptPromise.h"
 #include "modules/EventModules.h"
 #include "platform/heap/Handle.h"
@@ skipping 22 matching lines @@
     static PassRefPtrWillBeRawPtr<BeforeInstallPromptEvent> create(const AtomicString& name, const BeforeInstallPromptEventInit& init)
     {
         return adoptRefWillBeNoop(new BeforeInstallPromptEvent(name, init));
     }
 
     Vector<String> platforms() const;
     ScriptPromise userChoice(ScriptState*);
 
     virtual const AtomicString& interfaceName() const override;
 
+    // This is called after the site has first called preventDefault(), and now
+    // wishes to redispatch the event at a later point in their own context.

[mlamouri (slow - plz ping), 2015/06/06 21:40:55]

I don't think this comment is useful. prompt() is directly linked to the
bindings. It's merely boilerplate at that point.

+    void prompt();
+
 private:
     BeforeInstallPromptEvent();
     BeforeInstallPromptEvent(const AtomicString& name, const Vector<String>& platforms, int requestId, WebAppBannerClient*);
     BeforeInstallPromptEvent(const AtomicString& name, const BeforeInstallPromptEventInit&);
 
     Vector<String> m_platforms;
     ScriptPromise m_userChoice;
 
     int m_requestId;
     WebAppBannerClient* m_client;
+    bool m_redispatched;
 };
 
 DEFINE_TYPE_CASTS(BeforeInstallPromptEvent, Event, event, event->interfaceName() == EventNames::BeforeInstallPromptEvent, event.interfaceName() == EventNames::BeforeInstallPromptEvent);
 
 } // namespace blink
 
 #endif // BeforeInstallPromptEvent_h