Enable swarming on Linux ChromeOS bots.

scripts/slave/recipes/chromium.expected/full_chromium_chromiumos_Linux_ChromiumOS_Builder.json

 [
   {
     "cmd": [
       "python",
       "-u",
       "[BUILD]/scripts/slave/bot_update.py",
       "--master",
       "chromium.chromiumos",
       "--builder",
       "Linux ChromiumOS Builder",
@@ skipping 44 matching lines @@
       "@@@SET_BUILD_PROPERTY@got_v8_revision_git@\"801ada225ddc271c132c3a35f03975671d43e399\"@@@",
       "@@@SET_BUILD_PROPERTY@got_webrtc_revision_git@\"0f90628433546e61d9268596da93418c623137f4\"@@@",
       "@@@SET_BUILD_PROPERTY@got_swarming_client_revision_git@\"a0ee5d99f1d4b38ddaa4c759c837980b63b99566\"@@@",
       "@@@SET_BUILD_PROPERTY@got_revision_git@\"f27fede2220bcd326aee3e86ddfd4ebd0fe58cb9\"@@@"
     ]
   },
   {
     "cmd": [
       "python",
       "-u",
+      "[SLAVE_BUILD]/src/tools/swarming_client/swarming.py",
+      "--version"
+    ],
+    "name": "swarming.py --version",
+    "stdout": "/path/to/tmp/",
+    "~followup_annotations": [
+      "@@@STEP_TEXT@0.4.10@@@"
+    ]
+  },
+  {
+    "cmd": [
+      "python",
+      "-u",
       "[DEPOT_TOOLS]/gclient.py",
       "runhooks"
     ],
     "env": {
-      "GYP_DEFINES": "chromeos=1 component=static_library ffmpeg_branding=ChromeOS gomadir='[BUILD]/goma' proprietary_codecs=1 target_arch=x64 use_goma=1"
+      "GYP_DEFINES": "chromeos=1 component=static_library ffmpeg_branding=ChromeOS gomadir='[BUILD]/goma' proprietary_codecs=1 target_arch=x64 test_isolation_mode=archive test_isolation_outdir=https://isolateserver.appspot.com use_goma=1"
     },
     "name": "gclient runhooks"
   },
   {
     "cmd": [
       "python",
       "-u",
       "\nimport shutil\nimport sys\nshutil.copy(sys.argv[1], sys.argv[2])\n",
       "[SLAVE_BUILD]/src/testing/buildbot/chromium.chromiumos.json",
       "/path/to/tmp/json"
@@ skipping 60 matching lines @@
       "--build_revision",
       "170242",
       "--factory-properties",
       "{\"blamelist\": [\"cool_dev1337@chromium.org\", \"hax@chromium.org\"], \"buildername\": \"Linux ChromiumOS Builder\", \"buildnumber\": 571, \"mastername\": \"chromium.chromiumos\", \"parent_buildername\": null, \"recipe\": \"chromium\", \"slavename\": \"TestSlavename\", \"workdir\": \"/path/to/workdir/TestSlavename\"}",
       "--build-properties",
       "{\"blamelist\": [\"cool_dev1337@chromium.org\", \"hax@chromium.org\"], \"buildername\": \"Linux ChromiumOS Builder\", \"buildnumber\": 571, \"mastername\": \"chromium.chromiumos\", \"parent_buildername\": null, \"recipe\": \"chromium\", \"slavename\": \"TestSlavename\", \"workdir\": \"/path/to/workdir/TestSlavename\"}"
     ],
     "name": "package build"
   }
 ]