Sampling profiling thread should be joined in a FILE thread

chrome/test/base/tracing.cc

Index: chrome/test/base/tracing.cc
diff --git a/chrome/test/base/tracing.cc b/chrome/test/base/tracing.cc
index 5aa07e7e4d6f287e8de7564f6a258e09dd087e63..87e6aaa34342a684e1e3775b93c5ccb7320414ce 100644
--- a/chrome/test/base/tracing.cc
+++ b/chrome/test/base/tracing.cc
@@ -34,7 +34,6 @@ class InProcessTraceController {
     return content::TracingController::GetInstance()->EnableRecording(
         category_patterns, content::TracingController::DEFAULT_OPTIONS,
         content::TracingController::EnableRecordingDoneCallback());
-    return true;
   }
 
   bool BeginTracingWithWatch(const std::string& category_patterns,
@@ -44,11 +43,22 @@ class InProcessTraceController {
     DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
     DCHECK(num_occurrences > 0);
     watch_notification_count_ = num_occurrences;
-    return content::TracingController::GetInstance()->SetWatchEvent(
-        category_name, event_name,
-        base::Bind(&InProcessTraceController::OnWatchEventMatched,
-                   base::Unretained(this))) &&
-        BeginTracing(category_patterns);
+    if (!content::TracingController::GetInstance()->SetWatchEvent(
+            category_name, event_name,
+            base::Bind(&InProcessTraceController::OnWatchEventMatched,
+                       base::Unretained(this)))) {

[sky, 2014/01/06 18:14:24]

How do you know unretained is safe here and on 55? Also, don't you need to
cancel the watch?

[haraken, 2014/01/07 02:04:43]

InProcessTraceController is a Singleton, so I think it's safe to use unretained.
(Previous code is also using unretained.)
I don't know, but there has been no code about cancellation.

+      return false;
+    }
+    if (!content::TracingController::GetInstance()->EnableRecording(
+            category_patterns, content::TracingController::DEFAULT_OPTIONS,
+            base::Bind(&InProcessTraceController::OnEnableTracingComplete,
+                       base::Unretained(this)))) {
+      return false;
+    }
+
+    message_loop_runner_ = new content::MessageLoopRunner;
+    message_loop_runner_->Run();
+    return true;
   }
 
   bool WaitForWatchEvent(base::TimeDelta timeout) {
@@ -93,6 +103,10 @@ class InProcessTraceController {
  private:
   friend struct DefaultSingletonTraits<InProcessTraceController>;
 
+  void OnEnableTracingComplete() {
+    message_loop_runner_->Quit();
+  }
+
   void OnEndTracingComplete() {
     message_loop_runner_->Quit();
   }