Fix a crash bug on user script installation

chrome/renderer/user_script_slave.cc

 // Copyright (c) 2009 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 "chrome/renderer/user_script_slave.h"
 
 #include "app/resource_bundle.h"
 #include "base/command_line.h"
 #include "base/histogram.h"
 #include "base/logging.h"
@@ skipping 171 matching lines @@
       }
     }
     if (script->run_location() == location) {
       num_scripts += script->js_scripts().size();
       for (size_t j = 0; j < script->js_scripts().size(); ++j) {
         UserScript::File &file = script->js_scripts()[j];
         std::string content = file.GetContent().as_string();
 
         // We add this dumb function wrapper for standalone user script to
         // emulate what Greasemonkey does.
-        if (script->is_standalone()) {
+        if (script->is_standalone() || script->emulate_greasemonkey()) {
           content.insert(0, kUserScriptHead);
           content += kUserScriptTail;
         }
         sources.push_back(
             WebScriptSource(WebString::fromUTF8(content), file.url()));
       }
     }
 
     if (!sources.empty()) {
       int isolated_world_id = 0;
@@ skipping 35 matching lines @@
     if (num_scripts)
       UMA_HISTOGRAM_TIMES("Extensions.InjectIdle_Time", timer.Elapsed());
   } else {
     NOTREACHED();
   }
 
   LOG(INFO) << "Injected " << num_scripts << " scripts and " << num_css <<
       "css files into " << frame->url().spec().data();
   return true;
 }