Implement FeatureProvider for ExtensionAPI.

chrome/common/extensions/manifest_feature.h

+// Copyright (c) 2012 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 CHROME_COMMON_EXTENSIONS_MANIFEST_FEATURE_H_
+#define CHROME_COMMON_EXTENSIONS_MANIFEST_FEATURE_H_
+#pragma once
+
+#include "chrome/common/extensions/feature.h"
+
+namespace extensions {
+
+class ManifestFeature : public Feature {
+ public:
+  ManifestFeature();
+  virtual ~ManifestFeature();
+
+  virtual Feature::Availability IsAvailableToContext(
+      const Extension* extension,
+      Feature::Context context,
+      Feature::Platform platform) const OVERRIDE;
+};
+
+}  // extensions
+
+#endif  // CHROME_COMMON_EXTENSIONS_MANIFEST_FEATURE_H_