Add superficial unit test for PrintJob. That's a start....

base/thread_unittest.cc

 // Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/lock.h"
 #include "base/message_loop.h"
 #include "base/platform_test.h"
 #include "base/string_util.h"
 #include "base/thread.h"
 #include "testing/gtest/include/gtest/gtest.h"
@@ skipping 79 matching lines @@
     a.message_loop()->PostTask(FROM_HERE, new ToggleValue(&was_invoked));
   }
   EXPECT_TRUE(was_invoked);
 }
 
 TEST_F(ThreadTest, StopSoon) {
   Thread a("StopSoon");
   EXPECT_TRUE(a.Start());
   EXPECT_TRUE(a.message_loop());
   a.StopSoon();
-  EXPECT_FALSE(a.message_loop());
   a.StopSoon();
+  a.Stop();
   EXPECT_FALSE(a.message_loop());
 }
 
 TEST_F(ThreadTest, ThreadName) {
   Thread a("ThreadName");
   EXPECT_TRUE(a.Start());
   EXPECT_EQ("ThreadName", a.thread_name());
 }