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

extensions/renderer/module_system.cc

Index: extensions/renderer/module_system.cc
diff --git a/extensions/renderer/module_system.cc b/extensions/renderer/module_system.cc
index 6194b8ed4c4be059a5f298055d91df3b00bc4cab..f7b2ac7e6a266ebe017addbf2af5836025afcbde 100644
--- a/extensions/renderer/module_system.cc
+++ b/extensions/renderer/module_system.cc
@@ -6,6 +6,7 @@
 
 #include "base/bind.h"
 #include "base/command_line.h"
+#include "base/logging.h"
 #include "base/stl_util.h"
 #include "base/strings/string_util.h"
 #include "base/strings/stringprintf.h"
@@ -151,12 +152,10 @@ ModuleSystem::ModuleSystem(ScriptContext* context, SourceMap* source_map)
   }
 }
 
-ModuleSystem::~ModuleSystem() { Invalidate(); }
+ModuleSystem::~ModuleSystem() {
+}
 
 void ModuleSystem::Invalidate() {
-  if (!is_valid())
-    return;
-
   // Clear the module system properties from the global context. It's polite,
   // and we use this as a signal in lazy handlers that we no longer exist.
   {