Make functions being routed by NativeHandlers throw an exception if there is no ModuleSystem in the…

chrome/renderer/native_handler.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 "chrome/renderer/native_handler.h"
 
 #include "base/memory/linked_ptr.h"
 #include "base/logging.h"
+#include "chrome/renderer/module_system.h"
 #include "v8/include/v8.h"
 
 NativeHandler::NativeHandler()
     : object_template_(
         v8::Persistent<v8::ObjectTemplate>::New(v8::ObjectTemplate::New())) {
 }
 
 NativeHandler::~NativeHandler() {
   object_template_.Dispose();
 }
 
 v8::Handle<v8::Object> NativeHandler::NewInstance() {
   return object_template_->NewInstance();
 }
 
 // static
 v8::Handle<v8::Value> NativeHandler::Router(const v8::Arguments& args) {
+  // It is possible for JS code to execute after ModuleSystem has been deleted
+  // in which case the native handlers will also have been deleted, making
+  // HandlerFunction below point to freed memory.
+  if (!ModuleSystem::IsPresentInCurrentContext()) {
+    return v8::ThrowException(v8::Exception::Error(
+        v8::String::New("ModuleSystem has been deleted")));
+  }
   HandlerFunction* handler_function = static_cast<HandlerFunction*>(
       args.Data().As<v8::External>()->Value());
   return handler_function->Run(args);
 }
 
 void NativeHandler::RouteFunction(const std::string& name,
     const HandlerFunction& handler_function) {
   linked_ptr<HandlerFunction> function(new HandlerFunction(handler_function));
   // TODO(koz): Investigate using v8's MakeWeak() function instead of holding
   // on to these pointers here.
   handler_functions_.push_back(function);
   v8::Handle<v8::FunctionTemplate> function_template =
       v8::FunctionTemplate::New(Router,
           v8::External::New(function.get()));
   object_template_->Set(name.c_str(), function_template);
 }
 
 void NativeHandler::RouteStaticFunction(const std::string& name,
                                         const HandlerFunc handler_func) {
   v8::Handle<v8::FunctionTemplate> function_template =
       v8::FunctionTemplate::New(handler_func, v8::External::New(this));
   object_template_->Set(name.c_str(), function_template);
 }