chromium_tests: apply chromium.get_env() when running tests

scripts/slave/recipes/chromium_trybot.expected/compile_failure_without_patch_deapply_fn.json

 [
   {
     "cmd": [
       "python",
       "-u",
       "RECIPE_MODULE[depot_tools::bot_update]/resources/bot_update.py",
       "--master",
       "tryserver.chromium.linux",
       "--builder",
       "linux_chromium_rel_ng",
@@ skipping 416 matching lines @@
       "--test-launcher-summary-output",
       "/path/to/tmp/json",
       "--generate-json-file",
       "-o",
       "gtest-results/base_unittests",
       "--builder-name=linux_chromium_rel_ng",
       "--slave-name=TestSlavename",
       "--build-number=571",
       "base_unittests"
     ],
+    "env": {
+      "GOMA_SERVICE_ACCOUNT_JSON_FILE": "/creds/service_accounts/service-account-goma-client.json"
+    },
     "name": "base_unittests (with patch)",
     "~followup_annotations": [
       "step returned non-zero exit code: 1",
       "@@@STEP_TEXT@<br/>failures:<br/>Test.Two<br/>@@@",
       "@@@STEP_FAILURE@@@"
     ]
   },
   {
     "cmd": [
       "python",
@@ skipping 16 matching lines @@
       "--rietveld_server",
       "https://codereview.chromium.org",
       "--output_json",
       "/path/to/tmp/json",
       "--revision",
       "src@f27fede2220bcd326aee3e86ddfd4ebd0fe58cb9",
       "--force",
       "--output_manifest"
     ],
     "env": {
+      "GOMA_SERVICE_ACCOUNT_JSON_FILE": "/creds/service_accounts/service-account-goma-client.json",
       "PATH": "%(PATH)s:RECIPE_PACKAGE_REPO[depot_tools]"
     },
     "name": "bot_update (without patch)",
     "~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@  \"fixed_revisions\": {@@@",
       "@@@STEP_LOG_LINE@json.output@    \"src\": \"f27fede2220bcd326aee3e86ddfd4ebd0fe58cb9\"@@@",
       "@@@STEP_LOG_LINE@json.output@  }, @@@",
@@ skipping 135 matching lines @@
       "@@@STEP_WARNINGS@@@",
       "@@@SET_BUILD_PROPERTY@failure_type@\"INVALID_TEST_RESULTS\"@@@"
     ]
   },
   {
     "cmd": [
       "python",
       "-u",
       "import sys; sys.exit(1)"
     ],
+    "env": {
+      "GOMA_SERVICE_ACCOUNT_JSON_FILE": "/creds/service_accounts/service-account-goma-client.json"
+    },
     "name": "base_unittests",
     "~followup_annotations": [
       "step returned non-zero exit code: 1",
       "@@@STEP_TEXT@TEST RESULTS WERE INVALID@@@",
       "@@@STEP_FAILURE@@@",
       "@@@SET_BUILD_PROPERTY@failure_hash@\"212d0eb2385b1eaa828053689225258ece065725\"@@@"
     ]
   },
   {
     "name": "$result",
     "reason": "1 out of 1 aggregated steps failed. Failures: Step('base_unittests') failed with return_code 1",
     "status_code": 1
   }
 ]