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..8666ddaf75446a1ac12b8080cdf5aa0c263bd975 100644
--- a/public/platform/modules/app_banner/WebAppBannerClient.h
+++ b/public/platform/modules/app_banner/WebAppBannerClient.h
@@ -18,6 +18,9 @@ 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.
+    virtual void resolveEventRedispatch(int requestId) { }

[mlamouri (slow - plz ping), 2015/06/17 19:19:09]

I would rename that showAppBanner()

 };
 
 } // namespace blink