Support API aliases

tools/json_schema_compiler/test/features_test.json

 // Copyright 2016 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.
 {
   "alpha": {
     "channel": "stable",
     "contexts": ["blessed_extension"],
     "dependencies": ["permission:alpha"],
     "max_manifest_version": 1
   },
@@ skipping 56 matching lines @@
     "dependencies": ["permission:complex.child"]
   },
   "allEnum": {
     "channel": "beta",
     "extension_types": "all",
     "contexts": "all"
   },
   "uncompiled": {
     "contexts": ["blessed_extension"],
     "nocompile": true
+  },
+  "alias": {
+    "channel": "stable",
+    "contexts": ["blessed_extension"],
+    "source": "alias_source" 
+  },
+  "alias_source": {
+    "channel": "stable",
+    "contexts": ["blessed_extension"],
+    "alias": "alias"
+  },
+  "complex_alias": [{
+    "channel": "beta",
+    "contexts": ["blessed_extension"],
+    "source": "complex_alias_source"
+  }, {
+    "channel": "dev",
+    "contexts": ["webui"]
+  }],
+  "complex_alias_source": [{
+    "channel": "beta",
+    "contexts": ["blessed_extension"],
+    "alias": "complex_alias"
+  }, {
+    "channel": "dev",
+    "contexts": ["webui"]
+  }],
+  "parent_source" : {
+    "channel": "beta",
+    "contexts": ["blessed_extension"],
+    "alias": "parent_source.alias"
+  },
+  "parent_source.alias" : {
+    "channel": "beta",
+    "contexts": ["blessed_extension"],
+    "source": "parent_source"
   }
 }