Revert 106677 (caused several PPAPI test timeouts, see http://crbug.com/101154)

ppapi/thunk/ppb_instance_api.h

 // Copyright (c) 2011 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.
 
 #ifndef PPAPI_THUNK_INSTANCE_API_H_
 #define PPAPI_THUNK_INSTANCE_API_H_
 
 #include "ppapi/c/dev/ppb_url_util_dev.h"
 #include "ppapi/c/pp_completion_callback.h"
 #include "ppapi/c/ppb_instance.h"
 #include "ppapi/c/pp_bool.h"
 #include "ppapi/c/pp_size.h"
 #include "ppapi/c/private/ppb_instance_private.h"
 #include "ppapi/shared_impl/api_id.h"
 
-// Windows headers interfere with this file.
-#ifdef PostMessage
-#undef PostMessage
-#endif
-
 namespace ppapi {
 namespace thunk {
 
 class PPB_Instance_FunctionAPI {
  public:
   virtual ~PPB_Instance_FunctionAPI() {}
 
   virtual PP_Bool BindGraphics(PP_Instance instance, PP_Resource device) = 0;
   virtual PP_Bool IsFullFrame(PP_Instance instance) = 0;
 
@@ skipping 70 matching lines @@
   virtual PP_Var GetPluginInstanceURL(PP_Instance instance,
                                       PP_URLComponents_Dev* components) = 0;
 
   static const ApiID kApiID = API_ID_PPB_INSTANCE;
 };
 
 }  // namespace thunk
 }  // namespace ppapi
 
 #endif  // PPAPI_THUNK_INSTANCE_API_H_