Add the basic infrastructure for the Behavior feature type: BehaviorFeature and

extensions/common/api/_behavior_features.json

Index: extensions/common/api/_behavior_features.json
diff --git a/extensions/common/api/_behavior_features.json b/extensions/common/api/_behavior_features.json
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+++ b/extensions/common/api/_behavior_features.json
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+// Copyright 2014 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.
+
+// This features file defines switches used to control Extension behaviour,
+// typically whitelist configuration.
+//
+// See extensions/common/features/* to understand this file, in particular
+// feature.h, simple_feature.h, and base_feature_provider.h.
+//
+// To add a new whitelisted ID, SHA-1 it and force it to uppercase. In Bash:
+//
+// $ echo -n "aaaabbbbccccddddeeeeffffgggghhhh" | \
+// sha1sum | tr '[:lower:]' '[:upper:]'
+// 9A0417016F345C934A1A88F55CA17C05014EEEBA  -
+//
+// Google employees: please update http://go/chrome-api-whitelist to map
+// hashes back to ids.
+
+{
+  "whitelisted_for_incognito": {
+    "channel": "stable",
+    "extension_types": "all",
+    // This is "external_component" for legacy reasons; it should be
+    // unnecessary given there's a whitelist.
+    "location": "external_component",
+    "whitelist": [
+      "D5736E4B5CF695CB93A2FB57E4FDC6E5AFAB6FE2",  // http://crbug.com/312900
+      "D57DE394F36DC1C3220E7604C575D29C51A6C495",  // http://crbug.com/319444
+      "3F65507A3B39259B38C8173C6FFA3D12DF64CCE9"   // http://crbug.com/371562
+    ]
+  }
+}