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

chrome/browser/android/banners/app_banner_data_fetcher_android.h

Index: chrome/browser/android/banners/app_banner_data_fetcher_android.h
diff --git a/chrome/browser/android/banners/app_banner_data_fetcher_android.h b/chrome/browser/android/banners/app_banner_data_fetcher_android.h
index e059522e634851aaf6bd37b46f20af92c478e5cf..52ef8925d59d69cc78d8d348f586771605e5e8b6 100644
--- a/chrome/browser/android/banners/app_banner_data_fetcher_android.h
+++ b/chrome/browser/android/banners/app_banner_data_fetcher_android.h
@@ -26,15 +26,32 @@ class AppBannerDataFetcherAndroid : public AppBannerDataFetcher {
                         base::android::ScopedJavaLocalRef<jobject> app_data,
                         const GURL& image_url);
 
+  // Avoid compiler warning about hiding a virtual function with the same name.
+  using AppBannerDataFetcher::OnMessageReceived;
+
+  // WebContentsObserver override.
+  bool OnMessageReceived(const IPC::Message& message) override;
+
  protected:
   ~AppBannerDataFetcherAndroid() override;
 
   std::string GetBannerType() override;
   std::string GetAppIdentifier() override;
+
+  // AppBannerDataFetcher override. Queries the site's meta viewport tag to
+  // detect whether it is responsive, and proceeds by calling the base class
+  // implementation.
+  void HandleWebApp(content::WebContents* web_contents) override;
+
   void ShowBanner(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_;