Add "implemented_in" key in IDL schema compiler

tools/json_schema_compiler/test/idl_namespace_specific_implement_chromeos.idl

Index: tools/json_schema_compiler/test/idl_namespace_specific_implement_chromeos.idl
diff --git a/tools/json_schema_compiler/test/idl_namespace_specific_implement_chromeos.idl b/tools/json_schema_compiler/test/idl_namespace_specific_implement_chromeos.idl
new file mode 100644
index 0000000000000000000000000000000000000000..619e073fe9f731772c72c418869fb71a2f379d87
--- /dev/null
+++ b/tools/json_schema_compiler/test/idl_namespace_specific_implement_chromeos.idl
@@ -0,0 +1,11 @@
+// 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.
+
+// Tests the case of a namespace with specific implemented file on chromeos.
+
+[platforms=("chromeos"),
+ implemented_in="idl_namespace_specific_implement_chromeos.idl"]
+namespace idl_namespace_specific_implement_chromeos {
+
+};