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

chrome/browser/banners/app_banner_debug_log.h

Index: chrome/browser/banners/app_banner_debug_log.h
diff --git a/chrome/browser/banners/app_banner_debug_log.h b/chrome/browser/banners/app_banner_debug_log.h
index dab2733bd2081284e4754b5a8b131cdecdcbf6c4..65aa43d0060646ce64ff85eae037329f494d464f 100644
--- a/chrome/browser/banners/app_banner_debug_log.h
+++ b/chrome/browser/banners/app_banner_debug_log.h
@@ -27,12 +27,22 @@ extern const char kManifestMissingSuitableIcon[];
 extern const char kNotServedFromSecureOrigin[];
 extern const char kIgnoredNotSupportedOnAndroid[];
 extern const char kIgnoredNoId[];
+extern const char kAddMetaViewportTag[];
+extern const char kValidMetaViewportTagNotFound[];
+extern const char kMetaViewportTagContentsTooLong[];
+extern const char kMetaViewportTagNotResponsive[];
 
 // 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 message to the main console if a banner could not be shown due to a
+// missing or incorrect meta viewport tag on mobile
+// and the engagement checks have been bypassed.
+void OutputDeveloperMetaViewportErrorMessage(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,