Remove references to GClientKeywords.FromImpl from roll scripts

tools/roll_swiftshader.py

 #!/usr/bin/env python
 # Copyright 2015 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 argparse
 import collections
 import logging
 import os
 import re
@@ skipping 69 matching lines @@
 def _ParseDepsFile(filename):
   with open(filename, 'rb') as f:
     deps_content = f.read()
   return _ParseDepsDict(deps_content)
 
 
 def _ParseDepsDict(deps_content):
   local_scope = {}
   var = GClientKeywords.VarImpl({}, local_scope)
   global_scope = {
-    'From': GClientKeywords.FromImpl,
     'Var': var.Lookup,
     'deps_os': {},
   }
   exec(deps_content, global_scope, local_scope)
   return local_scope
 
 
 def _GenerateCLDescriptionCommand(swiftshader_current, swiftshader_new, bugs,
                                   tbr):
   def GetChangeString(current_hash, new_hash):
@@ skipping 311 matching lines @@
     logging.basicConfig(level=logging.ERROR)
 
   autoroller = AutoRoller(SRC_DIR)
   if args.abort:
     return autoroller.Abort()
   else:
     return autoroller.PrepareRoll(args.ignore_checks, args.tbr, args.commit)
 
 if __name__ == '__main__':
   sys.exit(main())