Fix how revision_cp is obtained in chromedriver recipe.

scripts/slave/recipes/chromedriver.expected/Android_ChromeDriver_Tests__dbg__test_failure.json

 [
   {
     "cmd": [
       "python",
       "-u",
       "RECIPE_MODULE[depot_tools::bot_update]/resources/bot_update.py",
       "--master",
       "chromium.fyi",
       "--builder",
       "Android ChromeDriver Tests (dbg)",
@@ skipping 912 matching lines @@
   },
   {
     "cmd": [],
     "name": "Upload Test Results Log"
   },
   {
     "cmd": [
       "python",
       "-u",
       "\nimport shutil\nimport sys\nshutil.copy(sys.argv[1], sys.argv[2])\n",
-      "{\"333333\": false}",
+      "{\"170242\": false}",
       "[TMP_BASE]/results_log_tmp_11/android_log.json"
     ],
     "name": "Upload Test Results Log.write results log to file android_log.json",
     "~followup_annotations": [
       "@@@STEP_NEST_LEVEL@1@@@"
     ]
   },
   {
     "cmd": [
       "python",
@@ skipping 133 matching lines @@
       "@@@STEP_LOG_LINE@python.inline@  os.remove(report)@@@",
       "@@@STEP_LOG_END@python.inline@@@"
     ]
   },
   {
     "name": "$result",
     "recipe_result": null,
     "status_code": 0
   }
 ]