Use FILE thread for disk operations in TraceSubscriberStdio

content/browser/trace_subscriber_stdio_unittest.cc

Index: content/browser/trace_subscriber_stdio_unittest.cc
===================================================================
--- content/browser/trace_subscriber_stdio_unittest.cc	(revision 120962)
+++ content/browser/trace_subscriber_stdio_unittest.cc	(working copy)
@@ -4,13 +4,20 @@
 
 #include "content/browser/trace_subscriber_stdio.h"
 
+#include "base/message_loop.h"
 #include "base/scoped_temp_dir.h"
+#include "base/threading/thread_restrictions.h"
+#include "content/browser/browser_thread_impl.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace {
 
 class TraceSubscriberStdioTest : public testing::Test {
  public:
+  TraceSubscriberStdioTest()
+      : file_thread_(content::BrowserThread::FILE, &loop_) {
+  }
+
   virtual void SetUp() {
     ASSERT_TRUE(trace_dir_.CreateUniqueTempDir());
     trace_file_ = trace_dir_.path().AppendASCII("trace.txt");
@@ -22,6 +29,8 @@
     return result;
   }
 
+  MessageLoop loop_;
+  content::BrowserThreadImpl file_thread_;
   ScopedTempDir trace_dir_;
   FilePath trace_file_;
 };
@@ -29,12 +38,20 @@
 }  // namespace
 
 TEST_F(TraceSubscriberStdioTest, CanWriteDataToFile) {
-  TraceSubscriberStdio subscriber(trace_file_);
-  subscriber.OnTraceDataCollected("[foo]");
-  subscriber.OnTraceDataCollected("[bar]");
-  EXPECT_TRUE(subscriber.IsValid());
+  std::string foo("foo");
+  std::string bar("bar");
 
-  subscriber.OnEndTracingComplete();
-  EXPECT_FALSE(subscriber.IsValid());
+  {
+    content::TraceSubscriberStdio subscriber(trace_file_);
+    subscriber.OnTraceDataCollected(
+        make_scoped_refptr(base::RefCountedString::TakeString(&foo)));
+    subscriber.OnTraceDataCollected(
+        make_scoped_refptr(base::RefCountedString::TakeString(&bar)));
+    subscriber.OnEndTracingComplete();
+  }
+
+  file_thread_.message_loop()->RunAllPending();
+  std::string result;
+  EXPECT_TRUE(file_util::ReadFileToString(trace_file_, &result));
+  EXPECT_EQ("[foo,bar]", result);
 }
-