Add "platforms" key in IDL schema compiler.

tools/json_schema_compiler/test/idl_namespace_chromeos.idl

Index: tools/json_schema_compiler/test/idl_namespace_chromeos.idl
diff --git a/chrome/test/data/extensions/api_test/webnavigation/failures/b.js b/tools/json_schema_compiler/test/idl_namespace_chromeos.idl
similarity index 59%
copy from chrome/test/data/extensions/api_test/webnavigation/failures/b.js
copy to tools/json_schema_compiler/test/idl_namespace_chromeos.idl
index 4956417ad1dac03f440608c60371b00a8734d640..421245e66d0884b36bbc5548acade889a4653be3 100644
--- a/chrome/test/data/extensions/api_test/webnavigation/failures/b.js
+++ b/tools/json_schema_compiler/test/idl_namespace_chromeos.idl
@@ -1,7 +1,10 @@
-// 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.
-
-onload = function() {
-  document.location = 'c.html';
-};
+// 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.
+
+// Tests the case of a namespace with chromeos platforms.
+
+[platforms=("chromeos")]
+namespace idl_namespace_chromeos {
+
+};