Keep the module in scope when executing scripts. This prevents a crash when the

webkit/plugins/ppapi/ppapi_plugin_instance.cc

 // 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.
 
 #include "webkit/plugins/ppapi/ppapi_plugin_instance.h"
 
 #include "base/logging.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/message_loop.h"
 #include "base/metrics/histogram.h"
@@ skipping 646 matching lines @@
   // Get the current frame to pass to the evaluate function.
   WebFrame* frame = container_->element().document().frame();
   if (!frame) {
     try_catch.SetException("No frame to execute script in.");
     return PP_MakeUndefined();
   }
 
   NPVariant result;
   bool ok = WebBindings::evaluate(NULL, frame->windowObject(), &np_script,
                                   &result);
+  // DANGER! |this| could be deleted at this point if the script removed the
+  // plugin from the DOM.
   if (!ok) {
     // TODO(brettw) bug 54011: The TryCatch isn't working properly and
     // doesn't actually catch this exception.
     try_catch.SetException("Exception caught");
     WebBindings::releaseVariantValue(&result);
     return PP_MakeUndefined();
   }
 
   PP_Var ret = Var::NPVariantToPPVar(this, &result);
   WebBindings::releaseVariantValue(&result);
@@ skipping 788 matching lines @@
   return found->second;
 }
 
 bool PluginInstance::IsFullPagePlugin() const {
   WebFrame* frame = container()->element().document().frame();
   return frame->view()->mainFrame()->document().isPluginDocument();
 }
 
 }  // namespace ppapi
 }  // namespace webkit