Use SequencedWorkerPool for disk operations in TraceSubscriberStdio.

base/debug/trace_event_unittest.cc

Index: base/debug/trace_event_unittest.cc
diff --git a/base/debug/trace_event_unittest.cc b/base/debug/trace_event_unittest.cc
index 9afd68b401a5dbe0a92e4aee926a0d2e6329188c..befd4e8b2473829f8f8756b5415135471953452c 100644
--- a/base/debug/trace_event_unittest.cc
+++ b/base/debug/trace_event_unittest.cc
@@ -42,7 +42,7 @@ class TraceEventTestFixture : public testing::Test {
   // up multiple times when testing AtExit. Use ManualTestSetUp for this.
   void ManualTestSetUp();
   void OnTraceDataCollected(
-      const scoped_refptr<TraceLog::RefCountedString>& events_str);
+      const scoped_refptr<base::RefCountedString>& events_str);
   DictionaryValue* FindMatchingTraceEntry(const JsonKeyValue* key_values);
   DictionaryValue* FindNamePhase(const char* name, const char* phase);
   DictionaryValue* FindNamePhaseKeyValue(const char* name,
@@ -91,11 +91,11 @@ void TraceEventTestFixture::ManualTestSetUp() {
 }
 
 void TraceEventTestFixture::OnTraceDataCollected(
-    const scoped_refptr<TraceLog::RefCountedString>& events_str) {
+    const scoped_refptr<base::RefCountedString>& events_str) {
   AutoLock lock(lock_);
   json_output_.json_output.clear();
   trace_buffer_.Start();
-  trace_buffer_.AddFragment(events_str->data);
+  trace_buffer_.AddFragment(events_str->data());
   trace_buffer_.Finish();
 
   scoped_ptr<Value> root;