Revert of Move the event attach/detach logic on unload from event.js to

extensions/renderer/module_system.h

Index: extensions/renderer/module_system.h
diff --git a/extensions/renderer/module_system.h b/extensions/renderer/module_system.h
index ad89524e54ec83c6bec4a23d904929201f64c32e..8b4a35ca45a1be49567df776c7f00924c16802c8 100644
--- a/extensions/renderer/module_system.h
+++ b/extensions/renderer/module_system.h
@@ -142,7 +142,6 @@
   }
 
  protected:
-  friend class ModuleSystemTestEnvironment;
   friend class ScriptContext;
   void Invalidate() override;
 
@@ -206,10 +205,6 @@
       const std::string& id,
       const std::vector<std::string>& dependencies) override;
 
-  // Marks any existing NativeHandler named |name| as clobbered.
-  // See |clobbered_native_handlers_|.
-  void ClobberExistingNativeHandler(const std::string& name);
-
   ScriptContext* context_;
 
   // A map from module names to the JS source for that module. GetSource()
@@ -227,15 +222,7 @@
   // tests.
   scoped_ptr<ExceptionHandler> exception_handler_;
 
-  // A set of native handlers that should actually be require()d as non-native
-  // handlers. This is used for tests to mock out native handlers in JS.
   std::set<std::string> overridden_native_handlers_;
-
-  // A list of NativeHandlers that have been clobbered, either due to
-  // registering a NativeHandler when one was already registered with the same
-  // name, or due to OverrideNativeHandlerForTest. This is needed so that they
-  // can be later Invalidated. It should only happen in tests.
-  std::vector<linked_ptr<NativeHandler>> clobbered_native_handlers_;
 
   base::WeakPtrFactory<ModuleSystem> weak_factory_;