Make the test NPAPI plugin not handle png

content/shell/tools/plugin/main.cpp

 // Copyright 2014 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.
 
 /*
  * Copyright (C) 2006, 2007 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
@@ skipping 824 matching lines @@
 NPError NPP_SetValue(NPP instance, NPNVariable variable, void *value)
 {
     PluginObject* obj = static_cast<PluginObject*>(instance->pdata);
     return obj->pluginTest->NPP_SetValue(variable, value);
 }
 
 #ifdef XP_UNIX
 extern "C"
 const char* NP_GetMIMEDescription(void)
 {
-    return "application/x-webkit-test-netscape:testnetscape:test netscape content;image/png:png:PNG image";
+    return "application/x-webkit-test-netscape:testnetscape:test netscape content";
 }
 
 extern "C"
 NPError NP_GetValue(NPP instance, NPPVariable variable, void* value)
 {
     return NPP_GetValue(instance, variable, value);
 }
 #endif