Remove unneeded extension_messages_browsertest.cc + cleanup.

chrome/renderer/extensions/app_bindings.cc

Index: chrome/renderer/extensions/app_bindings.cc
diff --git a/chrome/renderer/extensions/app_bindings.cc b/chrome/renderer/extensions/app_bindings.cc
index a5a902ae13a5199bd5db42089e63e43d0b9c3b2a..40857d9633ff19c8b8bb5dd797c82c2b9da8c16d 100644
--- a/chrome/renderer/extensions/app_bindings.cc
+++ b/chrome/renderer/extensions/app_bindings.cc
@@ -73,10 +73,7 @@ AppBindings::AppBindings(ExtensionDispatcher* dispatcher,
 
 v8::Handle<v8::Value> AppBindings::GetIsInstalled(
     const v8::Arguments& args) {
-  // TODO(aa): Hm, maybe ExtensionBindingsContext should have GetExtension()
-  // afterall?
-  const ::Extension* extension =
-      extension_dispatcher_->extensions()->GetByID(context_->extension_id());
+  const Extension* extension = context_->extension();
 
   // TODO(aa): Why only hosted app?
   bool result = extension && extension->is_hosted_app() &&