Add swarming support for MB (and the GN bots) in the chromium recipes.

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

 [
   {
     "cmd": [
       "python",
       "-u",
       "[BUILD]\\scripts\\slave\\kill_processes.py"
     ],
     "cwd": "[SLAVE_BUILD]",
     "name": "taskkill"
   },
@@ skipping 132 matching lines @@
     "name": "get compile targets for scripts",
     "~followup_annotations": [
       "@@@STEP_LOG_LINE@json.output@{}@@@",
       "@@@STEP_LOG_END@json.output@@@"
     ]
   },
   {
     "cmd": [
       "python",
       "-u",
-      "[BUILD]\\scripts\\slave\\cleanup_temp.py"
-    ],
-    "cwd": "[SLAVE_BUILD]",
-    "name": "cleanup_temp"
-  },
-  {
-    "cmd": [
-      "python",
-      "-u",
       "\nimport os, sys\nfrom common import chromium_utils\n\nif os.path.exists(sys.argv[1]):\n  chromium_utils.RemoveDirectory(sys.argv[1])\n",
       "[SLAVE_BUILD]\\src\\out\\Release"
     ],
     "cwd": "[SLAVE_BUILD]",
     "name": "rmtree build directory",
     "~followup_annotations": [
       "@@@STEP_LOG_LINE@python.inline@@@@",
       "@@@STEP_LOG_LINE@python.inline@import os, sys@@@",
       "@@@STEP_LOG_LINE@python.inline@from common import chromium_utils@@@",
       "@@@STEP_LOG_LINE@python.inline@@@@",
@@ skipping 18 matching lines @@
       "--build-properties",
       "{\"blamelist\": [\"cool_dev1337@chromium.org\", \"hax@chromium.org\"], \"buildername\": \"Win7 Tests (1)\", \"buildnumber\": 571, \"mastername\": \"chromium.win\", \"parent_buildername\": \"Win Builder\", \"recipe\": \"chromium\", \"slavename\": \"TestSlavename\", \"workdir\": \"/path/to/workdir/TestSlavename\"}"
     ],
     "cwd": "[SLAVE_BUILD]",
     "name": "extract build"
   },
   {
     "cmd": [
       "python",
       "-u",
+      "[BUILD]\\scripts\\slave\\cleanup_temp.py"
+    ],
+    "cwd": "[SLAVE_BUILD]",
+    "name": "cleanup_temp"
+  },
+  {
+    "cmd": [
+      "python",
+      "-u",
       "[BUILD]\\scripts\\slave\\chromium\\run_crash_handler.py",
       "--target",
       "Release"
     ],
     "cwd": "[SLAVE_BUILD]",
     "name": "start_crash_service"
   },
   {
     "allow_subannotations": true,
     "cmd": [
@@ skipping 75 matching lines @@
       "python",
       "-u",
       "[BUILD]\\scripts\\slave\\process_dumps.py",
       "--target",
       "Release"
     ],
     "cwd": "[SLAVE_BUILD]",
     "name": "process_dumps"
   }
 ]