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..2fd481cbbba2a926c2ecbe8d23d7630a7c263f88 100644
--- a/chrome/browser/extensions/stateful_external_extension_provider.h
+++ b/chrome/browser/extensions/stateful_external_extension_provider.h
@@ -20,6 +20,8 @@ class Version;
 // This provider can provide external extensions from two sources: crx files
 // and udpate URLs. The locations that the provider will report for these
 // are specified at the constructor.
+// Instances of this class are expected to be created and destroyed on the UI
+// thread and they are expecting public method calls from the FILE thread.
 class StatefulExternalExtensionProvider : public ExternalExtensionProvider {
  public:
   // Initialize the location for external extensions originating from crx
@@ -46,6 +48,12 @@ 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_;
 };