Cleanup: move base/platform_test.h -> testing/

base/worker_pool_unittest.cc

Index: base/worker_pool_unittest.cc
diff --git a/base/worker_pool_unittest.cc b/base/worker_pool_unittest.cc
index e3b5c16ef0cac03da58d243357140d8c39466949..e07e8ab11d9ae510fdc7790e22a9edafbaa2fc2f 100644
--- a/base/worker_pool_unittest.cc
+++ b/base/worker_pool_unittest.cc
@@ -2,11 +2,11 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include "base/platform_test.h"
 #include "base/task.h"
 #include "base/waitable_event.h"
 #include "base/worker_pool.h"
 #include "testing/gtest/include/gtest/gtest.h"
+#include "testing/platform_test.h"
 
 using base::WaitableEvent;