chromium_tests: apply chromium.get_env() when running tests

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

 [
   {
     "cmd": [
       "python",
       "-u",
       "RECIPE_PACKAGE_REPO[build]\\scripts\\slave\\kill_processes.py"
     ],
     "name": "taskkill"
   },
   {
@@ skipping 301 matching lines @@
       "--annotate=gtest",
       "--test-type=base_unittests",
       "--step-name=base_unittests",
       "--test-launcher-summary-output",
       "/path/to/tmp/json",
       "--builder-name=CrWinGoma",
       "--slave-name=TestSlavename",
       "--build-number=571",
       "base_unittests.exe"
     ],
+    "env": {
+      "GOMA_SERVICE_ACCOUNT_JSON_FILE": "C:\\creds\\service_accounts\\service-account-goma-client.json"
+    },
     "name": "base_unittests"
   },
   {
     "allow_subannotations": true,
     "cmd": [
       "python",
       "-u",
       "RECIPE_PACKAGE_REPO[build]\\scripts\\slave\\runtest.py",
       "--target",
       "Release",
       "--factory-properties",
       "{\"blamelist\": [\"cool_dev1337@chromium.org\", \"hax@chromium.org\"], \"build_data_dir\": \"[ROOT]\\\\build_data_dir\", \"buildername\": \"CrWinGoma\", \"buildnumber\": 571, \"mastername\": \"chromium.fyi\", \"parent_buildername\": null, \"recipe\": \"chromium\", \"slavename\": \"TestSlavename\", \"workdir\": \"/path/to/workdir/TestSlavename\"}",
       "--build-properties",
       "{\"blamelist\": [\"cool_dev1337@chromium.org\", \"hax@chromium.org\"], \"build_data_dir\": \"[ROOT]\\\\build_data_dir\", \"buildername\": \"CrWinGoma\", \"buildnumber\": 571, \"mastername\": \"chromium.fyi\", \"parent_buildername\": null, \"recipe\": \"chromium\", \"slavename\": \"TestSlavename\", \"workdir\": \"/path/to/workdir/TestSlavename\"}",
       "--annotate=gtest",
       "--test-type=content_unittests",
       "--step-name=content_unittests",
       "--test-launcher-summary-output",
       "/path/to/tmp/json",
       "--builder-name=CrWinGoma",
       "--slave-name=TestSlavename",
       "--build-number=571",
       "content_unittests.exe"
     ],
+    "env": {
+      "GOMA_SERVICE_ACCOUNT_JSON_FILE": "C:\\creds\\service_accounts\\service-account-goma-client.json"
+    },
     "name": "content_unittests"
   },
   {
     "cmd": [
       "python",
       "-u",
       "RECIPE_PACKAGE_REPO[build]\\scripts\\slave\\process_dumps.py",
       "--target",
       "Release"
     ],
+    "env": {
+      "GOMA_SERVICE_ACCOUNT_JSON_FILE": "C:\\creds\\service_accounts\\service-account-goma-client.json"
+    },
     "name": "process_dumps"
   },
   {
     "name": "$result",
     "recipe_result": null,
     "status_code": 0
   }
 ]