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

chrome/browser/banners/app_banner_debug_log.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_BANNERS_APP_BANNER_DEBUG_LOG_H_
 #define CHROME_BROWSER_BANNERS_APP_BANNER_DEBUG_LOG_H_
 
 #include <string>
 
 namespace content {
 class WebContents;
 }  // namespace content
 
 namespace banners {
 
 // Error message strings used to notify developers via the console.
 extern const char kRendererRequestCancel[];
 extern const char kManifestEmpty[];
 extern const char kCannotDetermineBestIcon[];
 extern const char kNoMatchingServiceWorker[];
 extern const char kNoIconAvailable[];
 extern const char kBannerAlreadyAdded[];
 extern const char kUserNavigatedBeforeBannerShown[];
 extern const char kStartURLNotValid[];
 extern const char kManifestMissingNameOrShortName[];
 extern const char kManifestMissingSuitableIcon[];
 extern const char kNotServedFromSecureOrigin[];
 extern const char kIgnoredNotSupportedOnAndroid[];
 extern const char kIgnoredNoId[];
+extern const char kMetaViewportTagError[];
 
 // Logs a message to the main console if a banner could not be shown
 // and the engagement checks have been bypassed.
 void OutputDeveloperNotShownMessage(content::WebContents* web_contents,
                                     const std::string& message);
 
 // Logs a debugging message to the main console if the engagement checks have
 // been bypassed.
 void OutputDeveloperDebugMessage(content::WebContents* web_contents,
                                  const std::string& message);
 
 }  // namespace banners
 
 #endif  // CHROME_BROWSER_BANNERS_APP_BANNER_DEBUG_LOG_H_