Ensure that SequencedWorkerPools in tests don't outlive their tests

content/browser/trace_subscriber_stdio_unittest.cc

Index: content/browser/trace_subscriber_stdio_unittest.cc
diff --git a/content/browser/trace_subscriber_stdio_unittest.cc b/content/browser/trace_subscriber_stdio_unittest.cc
index 6c8531c049d1d66ef4923f4d1c9f3e17bfebf6ee..df69f7d5a72c05a56823d409b2d23b0ff1ffbc96 100644
--- a/content/browser/trace_subscriber_stdio_unittest.cc
+++ b/content/browser/trace_subscriber_stdio_unittest.cc
@@ -10,7 +10,13 @@
 #include "content/public/browser/browser_thread.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
-TEST(TraceSubscriberStdioTest, CanWriteDataToFile) {
+class TraceSubscriberStdioTest : public ::testing::Test {
+ private:
+  // Needed by the blocking pool (but no need to pump it).
+  MessageLoop message_loop_;
+};
+
+TEST_F(TraceSubscriberStdioTest, CanWriteDataToFile) {
   ScopedTempDir trace_dir;
   ASSERT_TRUE(trace_dir.CreateUniqueTempDir());
   FilePath trace_file(trace_dir.path().AppendASCII("trace.txt"));