Change beforeinstallprompt event to take an array of platforms.

public/web/WebLocalFrame.h

 // Copyright 2014 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 WebLocalFrame_h
 #define WebLocalFrame_h
 
 #include "WebFrame.h"
 
 namespace blink {
@@ skipping 110 matching lines @@
     // selection to collapse. If the new extent is set to the same position as
     // the current base, this function will do nothing.
     virtual void moveRangeSelectionExtent(const WebPoint&, TextGranularity = CharacterGranularity) = 0;
 
     // Content Settings -------------------------------------------------------
 
     virtual void setContentSettingsClient(WebContentSettingsClient*) = 0;
 
     // App banner -------------------------------------------------------------
 
-    // Request to show an application install banner for the given |platform|.
+    // Request to show an application install banner for the given |platforms|.
     // The implementation can request the embedder to cancel the call by setting
     // |cancel| to true.
+    virtual void willShowInstallBannerPrompt(const WebVector<WebString>& platforms, WebAppBannerPromptReply*) = 0;
+
+    // Version of the above which takes a single platform.
+    // TODO(benwells): remove this once the chrome side has been updated.
     virtual void willShowInstallBannerPrompt(const WebString& platform, WebAppBannerPromptReply*) = 0;
 };
 
 } // namespace blink
 
 #endif // WebLocalFrame_h