Fix dart:html generated directory structure and unify file names between backends.

lib/html/scripts/systembase.py

Index: lib/html/scripts/systembase.py
diff --git a/lib/html/scripts/systembase.py b/lib/html/scripts/systembase.py
index bc096c7a3045e534c8a70901893eefe0c9e540f4..a63cf7ce87fc5166cbb2ab249ee76fc97ec28e71 100644
--- a/lib/html/scripts/systembase.py
+++ b/lib/html/scripts/systembase.py
@@ -49,18 +49,6 @@ class System(object):
 
   # Helper methods used by several systems.
 
-  def _ProcessCallback(self, interface, info, file_path):
-    """Generates a typedef for the callback interface."""
-    self._dart_interface_file_paths.append(file_path)
-    code = self._emitters.FileEmitter(file_path)
-
-    code.Emit(self._templates.Load('callback.darttemplate'))
-    code.Emit('typedef $TYPE $NAME($PARAMS);\n',
-              NAME=interface.id,
-              TYPE=DartType(info.type_name),
-              PARAMS=info.ParametersImplementationDeclaration(DartType))
-
-
   def _GenerateLibFile(self, lib_template, lib_file_path, file_paths,
                        **template_args):
     """Generates a lib file from a template and a list of files.