Temporary commit to evaluate perf impact of prototype CPU profiler

chrome/browser/chrome_browser_main.cc

Index: chrome/browser/chrome_browser_main.cc
diff --git a/chrome/browser/chrome_browser_main.cc b/chrome/browser/chrome_browser_main.cc
index e6c765f6576668a44210cf492ac3e598b4115425..b2c2e24ab9e0c0825d7d86f896b9a0a7d19b638d 100644
--- a/chrome/browser/chrome_browser_main.cc
+++ b/chrome/browser/chrome_browser_main.cc
@@ -996,6 +996,8 @@ int ChromeBrowserMainParts::PreCreateThreadsImpl() {
   // IOThread's initialization which happens in BrowserProcess:PreCreateThreads.
   SetupMetricsAndFieldTrials();
 
+  cpu_profiler_.Initialize(nullptr);
+
   // ChromeOS needs ResourceBundle::InitSharedInstance to be called before this.
   browser_process_->PreCreateThreads();
 
@@ -1650,6 +1652,8 @@ void ChromeBrowserMainParts::PostMainMessageLoopRun() {
   NOTREACHED();
 #else
 
+  cpu_profiler_.Stop();
+
   // Start watching for jank during shutdown. It gets disarmed when
   // |shutdown_watcher_| object is destructed.
   metrics::MetricsService::SetExecutionPhase(