test_isolation_outdir must be considered an opaque string, it could be an url.

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 37 matching lines @@
         # 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',
       ],
-      'action': [
-        'python',
-        '<(DEPTH)/tools/swarm_client/isolate.py',
-        '<(test_isolation_mode)',
-        '--outdir', '<(test_isolation_outdir)',
-        '--variable', 'PRODUCT_DIR', '<(PRODUCT_DIR)',
-        '--variable', 'OS', '<(OS)',
-        '--variable', 'chromeos', '<(chromeos)',
-        '--result', '<@(_outputs)',
-        '--isolate', '<(RULE_INPUT_PATH)',
-      ],
       'conditions': [
-        ["test_isolation_outdir!=''", {
+        ["test_isolation_outdir==''", {

[M-A Ruel, 2013/03/13 19:20:01]

changed to be more explicit.

           'action': [
-            '--outdir', '<(PRODUCT_DIR)/<(test_isolation_outdir)',
+            'python',
+            '<(DEPTH)/tools/swarm_client/isolate.py',
+            '<(test_isolation_mode)',
+            '--outdir', '<(PRODUCT_DIR)',
+            '--variable', 'PRODUCT_DIR', '<(PRODUCT_DIR)',
+            '--variable', 'OS', '<(OS)',
+            '--variable', 'chromeos', '<(chromeos)',
+            '--result', '<@(_outputs)',
+            '--isolate', '<(RULE_INPUT_PATH)',
+          ],
+        }, {
+          'action': [
+            'python',
+            '<(DEPTH)/tools/swarm_client/isolate.py',
+            '<(test_isolation_mode)',
+            '--outdir', '<(test_isolation_outdir)',
+            '--variable', 'PRODUCT_DIR', '<(PRODUCT_DIR)',
+            '--variable', 'OS', '<(OS)',
+            '--variable', 'chromeos', '<(chromeos)',
+            '--result', '<@(_outputs)',
+            '--isolate', '<(RULE_INPUT_PATH)',
           ],
         }],
         ['test_isolation_fail_on_missing == 0', {
             'action': ['--ignore_broken_items']
           },
         ],
       ],
       'msvs_cygwin_shell': 0,
     },
   ],
 }