Add DCHECKs to StatefulExternalExtensionProvider

chrome/browser/extensions/stateful_external_extension_provider.h

Index: chrome/browser/extensions/stateful_external_extension_provider.h
diff --git a/chrome/browser/extensions/stateful_external_extension_provider.h b/chrome/browser/extensions/stateful_external_extension_provider.h
index 141f45d4fb1d42fdb2cc7faafc8c11dd0634e0f4..f1462f8635918c1ea4b2b031fa1bdc4225999661 100644
--- a/chrome/browser/extensions/stateful_external_extension_provider.h
+++ b/chrome/browser/extensions/stateful_external_extension_provider.h
@@ -46,6 +46,12 @@ class StatefulExternalExtensionProvider : public ExternalExtensionProvider {
   // Location for external extensions that are provided by this provider from
   // update URLs.
   const Extension::Location download_location_;
+
+  // Stores the dictionary of external extensions internally. Takes ownership
+  // of |prefs|.
+  void set_prefs(DictionaryValue* prefs);
+
+ private:
   // Dictionary of the external extensions that are provided by this provider.
   scoped_ptr<DictionaryValue> prefs_;
 };