Fix top renderer crash. Extension can go away before Context. Duh.

BUG=123148


Review URL: http://codereview.chromium.org/10084016

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@132236 0039d316-1c4b-4281-b951-d872f2087c98

chrome/renderer/extensions/chrome_v8_context.h

@@ -39,7 +39,7 @@ class ChromeV8Context {
   }
 
   const Extension* extension() const {
-    return extension_;
+    return extension_.get();
   }
 
   WebKit::WebFrame* web_frame() const {
@@ -114,7 +114,7 @@ class ChromeV8Context {
 
   // The extension associated with this context, or NULL if there is none. This
   // might be a hosted app in the case that this context is hosting a web URL.
-  const Extension* extension_;
+  scoped_refptr<const Extension> extension_;
 
   // The type of context.
   extensions::Feature::Context context_type_;