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 7114301e0122160a1efe9b039301ef9e52a9b442..7b3820af0320c3db93107cb5c4d6c0f840b4ab12 100644
--- a/chrome/browser/android/banners/app_banner_data_fetcher_android.h
+++ b/chrome/browser/android/banners/app_banner_data_fetcher_android.h
@@ -26,6 +26,14 @@ class AppBannerDataFetcherAndroid : public AppBannerDataFetcher {
                         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;
 
@@ -35,6 +43,11 @@ class AppBannerDataFetcherAndroid : public AppBannerDataFetcher {
                                   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_;