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

extensions/renderer/script_context.h

Index: extensions/renderer/script_context.h
diff --git a/extensions/renderer/script_context.h b/extensions/renderer/script_context.h
index 10901e3efab3f1e874524b889e08d4e20b8c860d..b6c90f2c46f765723452a0450291768c6fc3ba6f 100644
--- a/extensions/renderer/script_context.h
+++ b/extensions/renderer/script_context.h
@@ -6,10 +6,8 @@
 #define EXTENSIONS_RENDERER_SCRIPT_CONTEXT_H_
 
 #include <string>
-#include <vector>
 
 #include "base/basictypes.h"
-#include "base/callback.h"
 #include "base/compiler_specific.h"
 #include "extensions/common/features/feature.h"
 #include "extensions/common/permissions/api_permission_set.h"
@@ -47,13 +45,9 @@
   // ModuleSystem.
   void Invalidate();
 
-  // Registers |observer| to be run when this context is invalidated. Closures
-  // are run immediately when Invalidate() is called, not in a message loop.
-  void AddInvalidationObserver(const base::Closure& observer);
-
   // Returns true if this context is still valid, false if it isn't.
   // A context becomes invalid via Invalidate().
-  bool is_valid() const { return is_valid_; }
+  bool is_valid() const { return !v8_context_.IsEmpty(); }
 
   v8::Handle<v8::Context> v8_context() const {
     return v8::Local<v8::Context>::New(isolate_, v8_context_);
@@ -156,14 +150,12 @@
   // extension.
   bool HasAPIPermission(APIPermission::ID permission) const;
 
+ protected:
+  // The v8 context the bindings are accessible to.
+  v8::Global<v8::Context> v8_context_;
+
  private:
   class Runner;
-
-  // Whether this context is valid.
-  bool is_valid_;
-
-  // The v8 context the bindings are accessible to.
-  v8::Global<v8::Context> v8_context_;
 
   // The WebFrame associated with this context. This can be NULL because this
   // object can outlive is destroyed asynchronously.
@@ -193,10 +185,6 @@
   // The set of capabilities granted to this context by extensions.
   APIPermissionSet content_capabilities_;
 
-  // A list of base::Closure instances as an observer interface for
-  // invalidation.
-  std::vector<base::Closure> invalidate_observers_;
-
   v8::Isolate* isolate_;
 
   GURL url_;