Adding shutdown tracing capabilities

chrome/browser/lifetime/application_lifetime.cc

Index: chrome/browser/lifetime/application_lifetime.cc
diff --git a/chrome/browser/lifetime/application_lifetime.cc b/chrome/browser/lifetime/application_lifetime.cc
index 503a0740226713866267851e18ad0b8dec5db6e2..1f0d5e88815945b7dd69fb051e6d7f5e5e4f913b 100644
--- a/chrome/browser/lifetime/application_lifetime.cc
+++ b/chrome/browser/lifetime/application_lifetime.cc
@@ -7,6 +7,7 @@
 #include "ash/shell.h"
 #include "base/bind.h"
 #include "base/command_line.h"
+#include "base/debug/trace_event.h"
 #include "base/logging.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/message_loop/message_loop.h"
@@ -125,6 +126,7 @@ void CloseAllBrowsers() {
 
 void AttemptUserExit() {

[DaveMoore, 2013/09/03 17:02:48]

Why can't you always start shutdown tracing here?

[Mr4D (OOO till 08-26), 2013/09/03 17:34:34]

As you have said yourself:
On other OS'ses then ChromeOS the user / running apps can stop the logging. If
there is a user interaction stopping the shutdown it does not make much sense to
trace that.

For ChromeOS on the other hand the state->CommitPendingWrite below might be of
interest.

[DaveMoore, 2013/09/03 20:24:11]

I would want that info in the trace, and then abort the write if the user ends
up not exiting.
On 2013/09/03 17:34:34, Mr4D wrote:

 #if defined(OS_CHROMEOS)
+  StartShutdownTracing();
   chromeos::BootTimesLoader::Get()->AddLogoutTimeMarker("LogoutStarted", false);
   // Write /tmp/uptime-logout-started as well.
   const char kLogoutStarted[] = "logout-started";
@@ -138,6 +140,7 @@ void AttemptUserExit() {
         state->GetString(prefs::kApplicationLocale) != owner_locale &&
         !state->IsManagedPreference(prefs::kApplicationLocale)) {
       state->SetString(prefs::kApplicationLocale, owner_locale);
+      TRACE_EVENT0("shutdown", "CommitPendingWrite");
       state->CommitPendingWrite();
     }
   }
@@ -154,6 +157,18 @@ void AttemptUserExit() {
 #endif
 }
 
+void StartShutdownTracing() {
+  const CommandLine& command_line = *CommandLine::ForCurrentProcess();
+  if (command_line.HasSwitch(switches::kTraceShutdown)) {
+    base::debug::CategoryFilter category_filter(
+        command_line.GetSwitchValueASCII(switches::kTraceShutdown));
+    base::debug::TraceLog::GetInstance()->SetEnabled(
+        category_filter,
+        base::debug::TraceLog::RECORD_UNTIL_FULL);
+  }
+  TRACE_EVENT0("shutdown", "AttemptUserExit");
+}
+
 // The Android implementation is in application_lifetime_android.cc
 #if !defined(OS_ANDROID)
 void AttemptRestart() {