Add a new gyp define to be used by the swarm master.

chrome/chrome_tests.gypi

 # 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.
 {
   'variables' : {
     'pyautolib_sources': [
       'app/chrome_command_ids.h',
       'app/chrome_dll_resource.h',
       'common/automation_constants.h',
       'common/pref_names.cc',
@@ skipping 2534 matching lines @@
           'action_name': 'isolate',
           'inputs': [
             '<@(isolate_dependency_tracked)',
           ],
           'outputs': [
             '<(PRODUCT_DIR)/unit_tests.results',
           ],
           'action': [
             'python',
             '../tools/isolate/isolate.py',
-            '--mode', '<(tests_run)',
+            '--mode', '<(test_isolation_mode)',
+            '--outdir', '<(test_isolation_outdir)',
             '--variable', 'PRODUCT_DIR', '<(PRODUCT_DIR)',
             '--variable', 'OS', '<(OS)',
             '--result', '<@(_outputs)',
             'unit_tests.isolate',
           ],
         },
       ],
     },
     {
       # Executable that runs each browser test in a new process.
@@ skipping 798 matching lines @@
           'action_name': 'isolate',
           'inputs': [
             '<@(isolate_dependency_tracked)',
           ],
           'outputs': [
             '<(PRODUCT_DIR)/browser_tests.results',
           ],
           'action': [
             'python',
             '../tools/isolate/isolate.py',
-            '--mode', '<(tests_run)',
+            '--mode', '<(test_isolation_mode)',
+            '--outdir', '<(test_isolation_outdir)',
             '--variable', 'PRODUCT_DIR', '<(PRODUCT_DIR)',
             '--variable', 'OS', '<(OS)',
             '--result', '<@(_outputs)',
             'browser_tests.isolate',
           ],
         },
       ],
     },
     {
       # Executable that runs each perf browser test in a new process.
@@ skipping 1322 matching lines @@
               # Use outputs of this action as inputs for the main target build.
               # Seems as a misnomer but makes this happy on Linux (scons).
               'process_outputs_as_sources': 1,
             },
           ],  # 'actions'
         },
       ]
     }],  # 'coverage!=0'
   ],  # 'conditions'
 }