Relanding this as the previous attempt failed due to build errors.

webkit/plugins/npapi/plugin_constants_win.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 WEBKIT_PLUGINS_NPAPI_PLUGIN_CONSTANTS_WIN_H_
 #define WEBKIT_PLUGINS_NPAPI_PLUGIN_CONSTANTS_WIN_H_
 
 #include "base/string16.h"
-#include "webkit/plugins/webkit_plugins_export.h"
 
 #if !defined(OS_WIN)
 #error "Windows-only header"
 #endif
 
 namespace webkit {
 namespace npapi {
 
 // The window class name for a plugin window.
 extern const char16 kNativeWindowClassName[];
 
 // The name of the window class name for the wrapper HWND around the actual
 // plugin window that's used when running in multi-process mode.  This window
 // is created on the browser UI thread.
-WEBKIT_PLUGINS_EXPORT extern const char16 kWrapperNativeWindowClassName[];
+extern const char16 kWrapperNativeWindowClassName[];
 
 // The name of the custom window message that the browser uses to tell the
 // plugin process to paint a window.
-WEBKIT_PLUGINS_EXPORT extern const char16 kPaintMessageName[];
+extern const char16 kPaintMessageName[];
 
 // The name of the registry key which NPAPI plugins update on installation.
-WEBKIT_PLUGINS_EXPORT extern const char16 kRegistryMozillaPlugins[];
+extern const char16 kRegistryMozillaPlugins[];
 
 extern const char16 kMozillaActiveXPlugin[];
-WEBKIT_PLUGINS_EXPORT extern const char16 kNewWMPPlugin[];
+extern const char16 kNewWMPPlugin[];
 extern const char16 kOldWMPPlugin[];
 extern const char16 kYahooApplicationStatePlugin[];
 extern const char16 kWanWangProtocolHandlerPlugin[];
 extern const char16 kFlashPlugin[];
 extern const char16 kAcrobatReaderPlugin[];
 extern const char16 kRealPlayerPlugin[];
 extern const char16 kSilverlightPlugin[];
 extern const char16 kJavaPlugin1[];
 extern const char16 kJavaPlugin2[];
 
 extern const char kGPUPluginMimeType[];
 
 }  // namespace npapi
 }  // namespace webkit
 
 #endif  // WEBKIT_PLUGINS_NPAPI_PLUGIN_PLUGIN_LIST_H_