Add new isolation mode "prepare".

build/isolate.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.
 
 # This file is meant to be included into a target to provide a rule
 # to "build" .isolate files into a .isolated file.
 #
 # To use this, create a gyp target with the following form:
 # 'conditions': [
 #   ['test_isolation_mode != "noop"', {
@@ skipping 45 matching lines @@
         # dependency. This improves the runtime of the build driver since it
         # doesn't have to stat() all these files.
         #
         # More importantly, it means that even if a isolate_dependency_tracked
         # file is missing, for example if a file was deleted and the .isolate
         # file was not updated, that won't break the build, especially in the
         # case where foo_tests_run is not built! This should be reenabled once
         # the switch-over to running tests on Swarm is completed.
         #'<@(isolate_dependency_tracked)',
       ],
-      'outputs': [
-        '<(PRODUCT_DIR)/<(RULE_INPUT_ROOT).isolated',
-      ],
+      'outputs': [],
       'action': [
         'python',
         '<(DEPTH)/tools/isolate_driver.py',
         '<(test_isolation_mode)',
-        '--isolated', '<@(_outputs)',
+        '--isolated', '<(PRODUCT_DIR)/<(RULE_INPUT_ROOT).isolated',
         '--isolate', '<(RULE_INPUT_PATH)',
 
         # Variables should use the -V FOO=<(FOO) form so frequent values,
         # like '0' or '1', aren't stripped out by GYP. Run 'isolate.py help' for
         # more details.
         #
         # This list needs to be kept in sync with the cmd line options
         # in src/build/android/pylib/gtest/setup.py.
 
         # Path variables are used to replace file paths when loading a .isolate
@@ skipping 27 matching lines @@
           'action': [
             '--extra-variable', 'mac_product_name', '<(mac_product_name)',
           ],
         }],
         ["test_isolation_outdir!=''", {
           'action': [ '--isolate-server', '<(test_isolation_outdir)' ],
         }],
         ['test_isolation_fail_on_missing == 0', {
           'action': ['--ignore_broken_items'],
         }],
+        ["test_isolation_mode == 'prepare'", {
+          'outputs': [
+            '<(PRODUCT_DIR)/<(RULE_INPUT_ROOT).isolated.gen.json',
+          ],
+        }, {
+          'outputs': [
+            '<(PRODUCT_DIR)/<(RULE_INPUT_ROOT).isolated',
+          ],
+        }],
       ],
     },
   ],
 }