MB: Add --isolate-map-file flag for overriding default isolate map.

tools/mb/mb_unittest.py

 #!/usr/bin/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.
 
 """Tests for mb.py."""
 
 import json
 import StringIO
 import os
 import sys
 import unittest
 
 import mb
 
 
 class FakeMBW(mb.MetaBuildWrapper):
   def __init__(self, win32=False):
     super(FakeMBW, self).__init__()
 
     # Override vars for test portability.
     if win32:
       self.chromium_src_dir = 'c:\\fake_src'
       self.default_config = 'c:\\fake_src\\tools\\mb\\mb_config.pyl'
+      self.default_isolate_map = ('c:\\fake_src\\testing\\buildbot\\'
+                                  'gn_isolate_map.pyl')
       self.platform = 'win32'
       self.executable = 'c:\\python\\python.exe'
       self.sep = '\\'
     else:
       self.chromium_src_dir = '/fake_src'
       self.default_config = '/fake_src/tools/mb/mb_config.pyl'
+      self.default_isolate_map = '/fake_src/testing/buildbot/gn_isolate_map.pyl'
       self.executable = '/usr/bin/python'
       self.platform = 'linux2'
       self.sep = '/'
 
     self.files = {}
     self.calls = []
     self.cmds = []
     self.cross_compile = None
     self.out = ''
     self.err = ''
@@ skipping 482 matching lines @@
     self.check(['lookup', '-c', 'fake_config'], mbw=mbw,
                ret=0,
                out=("GYP_DEFINES='foo=bar baz=1'\n"
                     "GYP_LINK_CONCURRENCY=1\n"
                     "LLVM_FORCE_HEAD_REVISION=1\n"
                     "python build/gyp_chromium -G output_dir=_path_\n"))
 
 
 if __name__ == '__main__':
   unittest.main()