Adds ModuleRegistryObserver interface

gin/modules/module_registry_observer.h

Index: gin/modules/module_registry_observer.h
diff --git a/gin/modules/module_registry_observer.h b/gin/modules/module_registry_observer.h
new file mode 100644
index 0000000000000000000000000000000000000000..a6b04f52c579ec13b1860fa0c63ed1d8e37e1a05
--- /dev/null
+++ b/gin/modules/module_registry_observer.h
@@ -0,0 +1,31 @@
+// Copyright 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef GIN_MODULES_MODULE_REGISTRY_OBSERVER_H_
+#define GIN_MODULES_MODULE_REGISTRY_OBSERVER_H_
+
+#include <string>
+#include <vector>
+
+#include "gin/gin_export.h"
+
+namespace gin {
+
+// Notified of interesting events from ModuleRegistry.
+class GIN_EXPORT ModuleRegistryObserver {
+ public:
+  // Called from AddPendingModule(). |id| is the id/name of the module and
+  // |dependencies| this list of modules |id| depends upon.
+  virtual void OnDidAddPendingModule(
+      const std::string& id,
+      const std::vector<std::string>& dependencies) = 0;
+
+ protected:
+  virtual ~ModuleRegistryObserver() {}
+};
+
+}  // namespace gin
+
+#endif  // GIN_MODULES_MODULE_REGISTRY_OBSERVER_H_
+