Clean up JSON Schema Compiler.

tools/json_schema_compiler/json_schema.py

 # 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.
 
 import copy
-import os
-import sys
 
 import json_parse
-import schema_util
 
 def DeleteNodes(item, delete_key):
   """Deletes the given nodes in item, recursively, that have |delete_key| as
   an attribute.
   """
   def HasKey(thing):
     return json_parse.IsDict(thing) and thing.get(delete_key, False)
 
   if json_parse.IsDict(item):
     toDelete = []
@@ skipping 20 matching lines @@
 _cache = {}
 
 def CachedLoad(filename):
   """Equivalent to Load(filename), but caches results for subsequent calls"""
   if filename not in _cache:
     _cache[filename] = Load(filename)
   # Return a copy of the object so that any changes a caller makes won't affect
   # the next caller.
   return copy.deepcopy(_cache[filename])