Add hooks for BeforeInstallPromptEvent to be redispatched.

public/platform/modules/app_banner/WebAppBannerClient.h

Index: public/platform/modules/app_banner/WebAppBannerClient.h
diff --git a/public/platform/modules/app_banner/WebAppBannerClient.h b/public/platform/modules/app_banner/WebAppBannerClient.h
index 57164c15b52ef7079d3f1c98746afcef22eb2e86..65c10c40eeb7245be01b30be0482a983adf5bc29 100644
--- a/public/platform/modules/app_banner/WebAppBannerClient.h
+++ b/public/platform/modules/app_banner/WebAppBannerClient.h
@@ -18,6 +18,16 @@ public:
 
     // Ownership of the callbacks is transferred to the client.
     virtual void registerBannerCallbacks(int requestId, WebAppBannerCallbacks*) = 0;
+
+    // Tell the client that the event is to be redispatched.
+    //
+    // TODO(dominickn) This method should be pure virtual. However, making it
+    // pure virtual causes compilation failures in tests. This is because the
+    // tests instantiate an AppBannerClient, which lives in the Chromium
+    // repository and inherits from this class. Once AppBannerClient has been
+    // updated to override this method, it will be made pure virtual. For now,
+    // it has a dummy do-nothing implementation.

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

nit: remove the comment. Not having the function pure virtual isn't a problem.
It's fairly common for Blink interfaces.
Alternatively, just leave a one-liner like "TODO(dominickn) make the method pure
virtual when implemented by Chromium."

+    virtual void resolveEventRedispatch(int requestId) { }
 };
 
 } // namespace blink