Add new app banner metrics using InstallableStatusCode.

chrome/browser/installable/installable_logging.h

 // Copyright 2016 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_INSTALLABLE_INSTALLABLE_LOGGING_H_
 #define CHROME_BROWSER_INSTALLABLE_INSTALLABLE_LOGGING_H_
 
 #include <string>
 
 namespace content {
 class WebContents;
 }
 
 // These values are a central reference for installability errors. The
 // InstallableManager will specify an InstallableErrorCode (or
-// NO_ERROR_DETECTED) in its result. Clients may also add their own error codes
-// to this list, and utilise LogErrorToConsole to write a message to the
-// devtools console.
-// TODO(dominickn) add an UMA metric for this enum.
+// NO_ERROR_DETECTED) in its result. Clients may also add their own error codes,
+// and utilise LogErrorToConsole to write a message to the devtools console.
+// This enum backs an UMA histogram, so it must be treated as append-only.
 enum InstallableErrorCode {

[benwells, 2016/08/11 04:47:34]

Nit: Maybe this type should be called something else, as not all of these are
errors.

   NO_ERROR_DETECTED,
   RENDERER_EXITING,
   RENDERER_CANCELLED,
   USER_NAVIGATED,
   NOT_IN_MAIN_FRAME,
   NOT_FROM_SECURE_ORIGIN,
   NO_MANIFEST,
   MANIFEST_EMPTY,
   START_URL_NOT_VALID,
   MANIFEST_MISSING_NAME_OR_SHORT_NAME,
   MANIFEST_DISPLAY_NOT_SUPPORTED,
   MANIFEST_MISSING_SUITABLE_ICON,
   NO_MATCHING_SERVICE_WORKER,
   NO_ACCEPTABLE_ICON,
   CANNOT_DOWNLOAD_ICON,
   NO_ICON_AVAILABLE,
   PLATFORM_NOT_SUPPORTED_ON_ANDROID,
   NO_ID_SPECIFIED,
   IDS_DO_NOT_MATCH,
+  ALREADY_INSTALLED,
+  INSUFFICIENT_ENGAGEMENT,
+  PACKAGE_NAME_OR_START_URL_EMPTY,
+  PREVIOUSLY_BLOCKED,
+  PREVIOUSLY_IGNORED,
+  SHOWING_NATIVE_APP_BANNER,
+  SHOWING_WEB_APP_BANNER,
+  FAILED_TO_CREATE_BANNER,
   MAX_ERROR_CODE,
 };
 
 // Logs a message associated with |code| with a parameter |param| to the
 // devtools console attached to |web_contents|. Does nothing if |web_contents|
 // is nullptr.
 void LogErrorToConsole(content::WebContents* web_contents,
                        InstallableErrorCode code,
                        const std::string& param);
 
 #endif  // CHROME_BROWSER_INSTALLABLE_INSTALLABLE_LOGGING_H_