Allow only responsive websites to install as a web app on mobile.

chrome/browser/android/banners/app_banner_data_fetcher_android.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 CHROME_BROWSER_ANDROID_BANNERS_APP_BANNER_DATA_FETCHER_ANDROID_H_
 #define CHROME_BROWSER_ANDROID_BANNERS_APP_BANNER_DATA_FETCHER_ANDROID_H_
 
 #include "base/android/jni_android.h"
 #include "chrome/browser/banners/app_banner_data_fetcher.h"
 
 namespace banners {
 
 // Fetches data required to show a banner for the URL currently shown by the
 // WebContents.  Extends the regular fetch to add support for Android apps.
 class AppBannerDataFetcherAndroid : public AppBannerDataFetcher {
  public:
   AppBannerDataFetcherAndroid(
       content::WebContents* web_contents,
       base::WeakPtr<Delegate> weak_delegate,
       int ideal_icon_size);
 
   // Saves information about the Android app being promoted by the current page,
   // then continues the creation pipeline.
   bool ContinueFetching(const base::string16& app_title,
                         const std::string& app_package,
                         base::android::ScopedJavaLocalRef<jobject> app_data,
                         const GURL& image_url);
 
+  using AppBannerDataFetcher::OnMessageReceived;
+
+  // WebContentsObserver override.
+  bool OnMessageReceived(const IPC::Message& message) override;
+
+  // Queries the site's meta viewport tag to detect whether it is responsive.
+  void Start(const GURL& validated_url) override;
+
  protected:
   ~AppBannerDataFetcherAndroid() override;
 
   std::string GetBannerType() override;
   std::string GetAppIdentifier() override;
   infobars::InfoBar* CreateBanner(const SkBitmap* icon,
                                   const base::string16& title) override;
 
  private:
+  void OnDidRetrieveMetaTagContent(bool success,
+                                   const std::string& tag_name,
+                                   const std::string& tag_content,
+                                   const GURL& expected_url);
+
   base::android::ScopedJavaGlobalRef<jobject> native_app_data_;
   std::string native_app_package_;
 
   DISALLOW_COPY_AND_ASSIGN(AppBannerDataFetcherAndroid);
 };
 
 }  // namespace banners
 
 #endif  // CHROME_BROWSER_ANDROID_BANNERS_APP_BANNER_DATA_FETCHER_ANDROID_H_