Move NPAPI test plugin to content/test/plugin.

content/test/plugin/plugin_thread_async_call_test.cc

Index: content/test/plugin/plugin_thread_async_call_test.cc
===================================================================
--- content/test/plugin/plugin_thread_async_call_test.cc	(revision 0)
+++ content/test/plugin/plugin_thread_async_call_test.cc	(working copy)
@@ -5,13 +5,13 @@
 #define UNIT_TEST  // To get the ShadowingAtExitManager.
 #include "base/at_exit.h"
 
-#include "webkit/plugins/npapi/test/plugin_thread_async_call_test.h"
+#include "content/test/plugin/plugin_thread_async_call_test.h"
 
 #include "base/bind.h"
 #include "base/message_loop/message_loop.h"
 #include "base/strings/string_util.h"
 #include "base/threading/thread.h"
-#include "webkit/plugins/npapi/test/plugin_client.h"
+#include "content/test/plugin/plugin_client.h"
 
 namespace NPAPIClient {