[Metrics] Move ExternalMetrics ownership to ChromeBrowserMainPartsChromeos

chrome/browser/chromeos/chrome_browser_main_chromeos.cc

Index: chrome/browser/chromeos/chrome_browser_main_chromeos.cc
diff --git a/chrome/browser/chromeos/chrome_browser_main_chromeos.cc b/chrome/browser/chromeos/chrome_browser_main_chromeos.cc
index a72b44deeec813a4cfac3347eae1f8101f363a92..4c6e10e0396e39114d0513d11e92243bf55d149f 100644
--- a/chrome/browser/chromeos/chrome_browser_main_chromeos.cc
+++ b/chrome/browser/chromeos/chrome_browser_main_chromeos.cc
@@ -702,7 +702,10 @@ void ChromeBrowserMainPartsChromeos::PreBrowserStart() {
   // -- This used to be in ChromeBrowserMainParts::PreMainMessageLoopRun()
   // -- just before MetricsService::LogNeedForCleanShutdown().
 
-  g_browser_process->metrics_service()->StartExternalMetrics();
+  // Start the external metrics service, which collects metrics from Chrome OS
+  // and passes them to the browser process.
+  external_metrics_ = new chromeos::ExternalMetrics;
+  external_metrics_->Start();
 
 #if defined(USE_X11)
   // Listen for system key events so that the user will be able to adjust the