Add histograms to the rendez-vous process (ProcessSingleton).

chrome/browser/chrome_browser_main.cc

 // Copyright (c) 2012 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/chrome_browser_main.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 1628 matching lines @@
     if (extension_startup_helper.PackExtension(parsed_command_line()))
       return content::RESULT_CODE_NORMAL_EXIT;
     return chrome::RESULT_CODE_PACK_EXTENSION_ERROR;
   }
 
   // When another process is running, use that process instead of starting a
   // new one. NotifyOtherProcess will currently give the other process up to
   // 20 seconds to respond. Note that this needs to be done before we attempt
   // to read the profile.
   notify_result_ = process_singleton_->NotifyOtherProcessOrCreate();
+  UMA_HISTOGRAM_ENUMERATION("Chrome.ProcessSingleton.NotifyResult",
+                            notify_result_,
+                            ProcessSingleton::NUM_NOTIFY_RESULTS);
   switch (notify_result_) {
     case ProcessSingleton::PROCESS_NONE:
       // No process already running, fall through to starting a new one.
       g_browser_process->platform_part()->PlatformSpecificCommandLineProcessing(
           *base::CommandLine::ForCurrentProcess());
       break;
 
     case ProcessSingleton::PROCESS_NOTIFIED:
 #if defined(OS_POSIX) && !defined(OS_MACOSX)
       // On POSIX systems, print a message notifying the process is running.
@@ skipping 13 matching lines @@
       return chrome::RESULT_CODE_PROFILE_IN_USE;
 
     case ProcessSingleton::LOCK_ERROR:
       LOG(ERROR) << "Failed to create a ProcessSingleton for your profile "
                     "directory. This means that running multiple instances "
                     "would start multiple browser processes rather than "
                     "opening a new window in the existing process. Aborting "
                     "now to avoid profile corruption.";
       return chrome::RESULT_CODE_PROFILE_IN_USE;
 
-    default:
+    case ProcessSingleton::NUM_NOTIFY_RESULTS:

[bcwhite, 2016/10/07 16:17:44]

Why this change?

[gab, 2016/10/07 16:34:14]

Because it's better to enumerate all cases than to have a default switch as it
allows clang to warn when a switch doesn't handle a new enum value.

[bcwhite, 2016/10/07 16:59:45]

Acknowledged.

       NOTREACHED();
+      break;
   }
 #endif  // !defined(OS_ANDROID)
 
   // Handle special early return paths (which couldn't be processed even earlier
   // as they require the process singleton to be held) first.
 
   std::string try_chrome =
       parsed_command_line().GetSwitchValueASCII(switches::kTryChromeAgain);
   if (!try_chrome.empty()) {
 #if defined(OS_WIN)
@@ skipping 531 matching lines @@
   chromeos::CrosSettings::Shutdown();
 #endif  // defined(OS_CHROMEOS)
 #endif  // defined(OS_ANDROID)
 }
 
 // Public members:
 
 void ChromeBrowserMainParts::AddParts(ChromeBrowserMainExtraParts* parts) {
   chrome_extra_parts_.push_back(parts);
 }