Make the root_namespace argument to json_schema_compiler.gypi a string

tools/json_schema_compiler/features_h_generator.py

Index: tools/json_schema_compiler/features_h_generator.py
diff --git a/tools/json_schema_compiler/features_h_generator.py b/tools/json_schema_compiler/features_h_generator.py
index 025f734fd9542d0623e8b938ee26e4391587f38c..4198bb4b1d92e8c35893536f2d4315273b2f8d9e 100644
--- a/tools/json_schema_compiler/features_h_generator.py
+++ b/tools/json_schema_compiler/features_h_generator.py
@@ -32,8 +32,12 @@ class _Generator(object):
       .Append(cpp_util.GENERATED_FEATURE_MESSAGE % self._source_file)
       .Append()
     )
-    ifndef_name = cpp_util.GenerateIfndefName(self._source_file_filename,
-                                              self._class_name)
+
+    # Hack: for the purpose of gyp the header file will always be the source
+    # file with its file extension replaced by '.h'. Assume so.
+    output_file = os.path.splitext(self._namespace.source_file)[0] + '.h'
+    ifndef_name = cpp_util.GenerateIfndefName(output_file)
+
     (c.Append('#ifndef %s' % ifndef_name)
       .Append('#define %s' % ifndef_name)
       .Append()