Add missing base/threading/platform_thread import.

TBR=ajwong@chromium.org

Review URL: https://chromiumcodereview.appspot.com/10447011

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@138761 0039d316-1c4b-4281-b951-d872f2087c98

remoting/host/clipboard_win.cc

@@ -11,6 +11,7 @@
 #include "base/logging.h"
 #include "base/process_util.h"
 #include "base/string16.h"
+#include "base/threading/platform_thread.h"
 #include "base/utf_string_conversions.h"
 #include "base/win/scoped_hglobal.h"
 #include "base/win/windows_version.h"