Decouple killbit testing from external extension providers

chrome/browser/extensions/extension_prefs.h

Index: chrome/browser/extensions/extension_prefs.h
diff --git a/chrome/browser/extensions/extension_prefs.h b/chrome/browser/extensions/extension_prefs.h
index 6245edac68f2ea73e5c6496f1088e1acb0f99533..90f1a7f2027df8c5bd0327de754b0862739f78d0 100644
--- a/chrome/browser/extensions/extension_prefs.h
+++ b/chrome/browser/extensions/extension_prefs.h
@@ -47,8 +47,9 @@ class ExtensionPrefs {
   // aware of the internal structure of the preferences.
   DictionaryValue* CopyCurrentExtensions();
 
-  // Populate |killed_ids| with extension ids that have been killed.
-  void GetKilledExtensionIds(std::set<std::string>* killed_ids);
+  // Returns true if the specified extension has an entry in prefs
+  // and its killbit is on.
+  bool IsExtensionKilled(const std::string& id);
 
   // Get the order that toolstrip URLs appear in the shelf.
   typedef std::vector<GURL> URLList;