chromium_tests: fix crash in deapply_patch on got_webkit_revision

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

 [
   {
     "cmd": [
       "python",
       "-u",
       "[BUILD]\\scripts\\slave\\kill_processes.py"
     ],
     "cwd": "[SLAVE_BUILD]",
     "name": "taskkill"
   },
   {
     "cmd": [
       "python",
       "-u",
       "[BUILD]\\scripts\\slave\\bot_update.py",
       "--master",
       "chromium.webkit",
       "--builder",
       "WebKit XP",
       "--slave",
       "TestSlavename",
       "--spec",
       "cache_dir = None\nsolutions = [{'custom_vars': {'googlecode_url': 'svn://svn-mirror.golo.chromium.org/%s', 'nacl_trunk': 'svn://svn-mirror.golo.chromium.org/native_client/trunk', 'sourceforge_url': 'svn://svn-mirror.golo.chromium.org/%(repo)s', 'webkit_trunk': 'svn://svn-mirror.golo.chromium.org/blink/trunk'}, 'deps_file': 'DEPS', 'managed': True, 'name': 'src', 'url': 'svn://svn-mirror.golo.chromium.org/chrome/trunk/src'}]",
       "--root",
       "src",
       "--revision_mapping_file",
-      "{\"src\": \"got_revision\", \"src/native_client\": \"got_nacl_revision\", \"src/third_party/WebKit\": \"got_webkit_revision\", \"src/third_party/webrtc\": \"got_webrtc_revision\", \"src/tools/swarming_client\": \"got_swarming_client_revision\", \"src/v8\": \"got_v8_revision\"}",
+      "{\"src\": \"got_revision\", \"src/native_client\": \"got_nacl_revision\", \"src/third_party/webrtc\": \"got_webrtc_revision\", \"src/tools/swarming_client\": \"got_swarming_client_revision\", \"src/v8\": \"got_v8_revision\"}",
       "--output_json",
       "/path/to/tmp/json",
       "--revision",
       "src@7496f63cbefd34b2d791022fbad64a82838a3f3f",
       "--revision",
       "src/third_party/WebKit@191275"
     ],
     "cwd": "[SLAVE_BUILD]",
     "name": "bot_update",
     "~followup_annotations": [
       "@@@STEP_TEXT@Some step text@@@",
       "@@@STEP_LOG_LINE@json.output@{@@@",
       "@@@STEP_LOG_LINE@json.output@  \"did_run\": true, @@@",
       "@@@STEP_LOG_LINE@json.output@  \"patch_failure\": false, @@@",
       "@@@STEP_LOG_LINE@json.output@  \"patch_root\": \"src\", @@@",
       "@@@STEP_LOG_LINE@json.output@  \"properties\": {@@@",
       "@@@STEP_LOG_LINE@json.output@    \"got_nacl_revision\": \"d998e125e8253980d76e269b7982aeeefc1b9b50\", @@@",
       "@@@STEP_LOG_LINE@json.output@    \"got_nacl_revision_cp\": \"refs/heads/master@{#274981}\", @@@",
       "@@@STEP_LOG_LINE@json.output@    \"got_revision\": \"f27fede2220bcd326aee3e86ddfd4ebd0fe58cb9\", @@@",
       "@@@STEP_LOG_LINE@json.output@    \"got_revision_cp\": \"refs/heads/master@{#170242}\", @@@",
       "@@@STEP_LOG_LINE@json.output@    \"got_swarming_client_revision\": \"a0ee5d99f1d4b38ddaa4c759c837980b63b99566\", @@@",
       "@@@STEP_LOG_LINE@json.output@    \"got_swarming_client_revision_cp\": \"refs/heads/master@{#276089}\", @@@",
       "@@@STEP_LOG_LINE@json.output@    \"got_v8_revision\": \"801ada225ddc271c132c3a35f03975671d43e399\", @@@",
       "@@@STEP_LOG_LINE@json.output@    \"got_v8_revision_cp\": \"refs/heads/master@{#43426}\", @@@",
-      "@@@STEP_LOG_LINE@json.output@    \"got_webkit_revision\": \"5e2293dffc3cd07d37fbedea3b500f0eb650614d\", @@@",
-      "@@@STEP_LOG_LINE@json.output@    \"got_webkit_revision_cp\": \"refs/heads/master@{#124383}\", @@@",
       "@@@STEP_LOG_LINE@json.output@    \"got_webrtc_revision\": \"0f90628433546e61d9268596da93418c623137f4\", @@@",
       "@@@STEP_LOG_LINE@json.output@    \"got_webrtc_revision_cp\": \"refs/heads/master@{#120644}\"@@@",
       "@@@STEP_LOG_LINE@json.output@  }, @@@",
       "@@@STEP_LOG_LINE@json.output@  \"root\": \"src\", @@@",
       "@@@STEP_LOG_LINE@json.output@  \"step_text\": \"Some step text\"@@@",
       "@@@STEP_LOG_LINE@json.output@}@@@",
       "@@@STEP_LOG_END@json.output@@@",
       "@@@SET_BUILD_PROPERTY@got_nacl_revision@\"d998e125e8253980d76e269b7982aeeefc1b9b50\"@@@",
-      "@@@SET_BUILD_PROPERTY@got_webkit_revision@\"5e2293dffc3cd07d37fbedea3b500f0eb650614d\"@@@",
       "@@@SET_BUILD_PROPERTY@got_swarming_client_revision@\"a0ee5d99f1d4b38ddaa4c759c837980b63b99566\"@@@",
       "@@@SET_BUILD_PROPERTY@got_webrtc_revision@\"0f90628433546e61d9268596da93418c623137f4\"@@@",
       "@@@SET_BUILD_PROPERTY@got_revision@\"f27fede2220bcd326aee3e86ddfd4ebd0fe58cb9\"@@@",
       "@@@SET_BUILD_PROPERTY@got_nacl_revision_cp@\"refs/heads/master@{#274981}\"@@@",
-      "@@@SET_BUILD_PROPERTY@got_webkit_revision_cp@\"refs/heads/master@{#124383}\"@@@",
       "@@@SET_BUILD_PROPERTY@got_v8_revision@\"801ada225ddc271c132c3a35f03975671d43e399\"@@@",
       "@@@SET_BUILD_PROPERTY@got_v8_revision_cp@\"refs/heads/master@{#43426}\"@@@",
       "@@@SET_BUILD_PROPERTY@got_swarming_client_revision_cp@\"refs/heads/master@{#276089}\"@@@",
       "@@@SET_BUILD_PROPERTY@got_webrtc_revision_cp@\"refs/heads/master@{#120644}\"@@@",
       "@@@SET_BUILD_PROPERTY@got_revision_cp@\"refs/heads/master@{#170242}\"@@@"
     ]
   },
   {
     "cmd": [
       "python",
@@ skipping 183 matching lines @@
       "python",
       "-u",
       "[BUILD]\\scripts\\slave\\process_dumps.py",
       "--target",
       "Release"
     ],
     "cwd": "[SLAVE_BUILD]",
     "name": "process_dumps"
   }
 ]