Profiler-instrumentation of the startup time.

Before the instrumentation, startup time wasn't reported in profiler data.

Profiling it will allow the genre of detailed analysis of the startup time via jankiness investigations.

This change requires temporarily initializing tracking earlier than usual. Thie will either removed once the investigations complete, or will be officially converted to permanent code.

BUG=453640

Review URL: https://codereview.chromium.org/866403008

Cr-Commit-Position: refs/heads/master@{#314179}

chrome/app/chrome_main.cc

@@ -4,6 +4,8 @@
 
 #include "chrome/app/chrome_main_delegate.h"
 
+#include "base/profiler/scoped_tracker.h"
+#include "chrome/common/chrome_version_info.h"
 #include "content/public/app/content_main.h"
 
 #if defined(OS_WIN)
@@ -63,6 +65,22 @@ int ChromeMain(int argc, const char** argv) {
   params.argv = argv;
 #endif
 
+  // TODO(vadimt): Remove the switch statement below once crbug.com/453640 is
+  // fixed.
+  // Enable profiler instrumentation depending on the channel.
+  switch (chrome::VersionInfo::GetChannel()) {
+    case chrome::VersionInfo::CHANNEL_UNKNOWN:
+    case chrome::VersionInfo::CHANNEL_CANARY:
+      tracked_objects::ScopedTracker::Enable();
+      break;
+
+    case chrome::VersionInfo::CHANNEL_DEV:
+    case chrome::VersionInfo::CHANNEL_BETA:
+    case chrome::VersionInfo::CHANNEL_STABLE:
+      // Don't enable instrumentation.
+      break;
+  }
+
   int rv = content::ContentMain(params);
 
 #if defined(OS_WIN)

content/browser/browser_main_runner.cc

@@ -10,7 +10,9 @@
 #include "base/logging.h"
 #include "base/metrics/histogram.h"
 #include "base/metrics/statistics_recorder.h"
+#include "base/profiler/scoped_tracker.h"
 #include "base/trace_event/trace_event.h"
+#include "base/tracked_objects.h"
 #include "content/browser/browser_main_loop.h"
 #include "content/browser/browser_shutdown_profile_dumper.h"
 #include "content/browser/notification_service_impl.h"
@@ -126,6 +128,13 @@ class BrowserMainRunnerImpl : public BrowserMainRunner {
   }
 
   int Initialize(const MainFunctionParams& parameters) override {
+    // TODO(vadimt): Remove all tracked_objects references below once
+    // crbug.com/453640 is fixed.
+    tracked_objects::ThreadData::InitializeThreadContext("CrBrowserMain");
+
+    tracked_objects::ScopedTracker tracking_profile(
+        FROM_HERE_WITH_EXPLICIT_FUNCTION("BrowserMainRunnerImpl::Initialize"));
+
     TRACE_EVENT0("startup", "BrowserMainRunnerImpl::Initialize");
     // On Android we normally initialize the browser in a series of UI thread
     // tasks. While this is happening a second request can come from the OS or