Add UMA histogram to track the various sources that request the feedback app

chrome/browser/ui/webui/settings/about_handler.cc

 // 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.
 
 #include "chrome/browser/ui/webui/settings/about_handler.h"
 
 #include <stddef.h>
 
 #include <string>
 
@@ skipping 422 matching lines @@
 #if defined(OS_MACOSX)
 void AboutHandler::PromoteUpdater(const base::ListValue* args) {
   version_updater_->PromoteUpdater();
 }
 #endif
 
 void AboutHandler::HandleOpenFeedbackDialog(const base::ListValue* args) {
   DCHECK(args->empty());
   Browser* browser =
       chrome::FindBrowserWithWebContents(web_ui()->GetWebContents());
-  chrome::OpenFeedbackDialog(browser);
+  chrome::OpenFeedbackDialog(browser,
+                             chrome::kFeedbackSourceMdSettingsAboutPage);
 }
 
 void AboutHandler::HandleOpenHelpPage(const base::ListValue* args) {
   DCHECK(args->empty());
   Browser* browser =
       chrome::FindBrowserWithWebContents(web_ui()->GetWebContents());
   chrome::ShowHelp(browser, chrome::HELP_SOURCE_WEBUI);
 }
 
 #if defined(OS_CHROMEOS)
@@ skipping 190 matching lines @@
       label_dir_path.AppendASCII(kRegulatoryLabelImageFilename).MaybeAsASCII();
   std::string url =
       std::string("chrome://") + chrome::kChromeOSAssetHost + "/" + image_path;
   regulatory_info->SetString("url", url);
 
   ResolveJavascriptCallback(base::Value(callback_id), *regulatory_info);
 }
 #endif  // defined(OS_CHROMEOS)
 
 }  // namespace settings