Revert of Replace NPObject usage in ppapi with gin

ppapi/tests/test_post_message.cc

 // Copyright (c) 2012 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.
 
 #include "ppapi/tests/test_post_message.h"
 
 #include <string.h>
 #include <algorithm>
 #include <map>
 #include <sstream>
@@ skipping 154 matching lines @@
   js_code += "var plugin = document.getElementById('plugin');"
              "plugin.removeEventListener('message',"
              "                           plugin.wait_for_messages_handler);"
              "delete plugin.wait_for_messages_handler;";
   instance_->EvalScript(js_code);
 }
 
 bool TestPostMessage::Init() {
   bool success = CheckTestingInterface();
 
-  // Add a post condition to tests which caches the postMessage function and
-  // then calls it after the instance is destroyed. The ensures that no UAF
-  // occurs because the MessageChannel may still be alive after the plugin
-  // instance is destroyed (it will get garbage collected eventually).
-  instance_->EvalScript("window.pluginPostMessage = "
-                        "document.getElementById('plugin').postMessage");
-  instance_->AddPostCondition("window.pluginPostMessage('') === undefined");
-
   // Set up a special listener that only responds to a FINISHED_WAITING string.
   // This is for use by WaitForMessages.
   std::string js_code;
   // Note the following code is dependent on some features of test_case.html.
   // E.g., it is assumed that the DOM element where the plugin is embedded has
   // an id of 'plugin', and there is a function 'IsTestingMessage' that allows
   // us to ignore the messages that are intended for use by the testing
   // framework itself.
   js_code += "var plugin = document.getElementById('plugin');"
              "var wait_for_messages_handler = function(message_event) {"
@@ skipping 716 matching lines @@
     ASSERT_TRUE(received_value <= kThreadsToRun);
     ++received_counts[received_value];
   }
   ASSERT_EQ(expected_counts, received_counts);
 
   message_data_.clear();
   ASSERT_TRUE(ClearListeners());
 
   PASS();
 }