WebRTC: Enable MB on our remaining Chromium builders.

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

 [
   {
     "cmd": [
       "python",
       "-u",
       "RECIPE_PACKAGE_REPO[build]\\scripts\\slave\\kill_processes.py"
     ],
     "name": "taskkill"
   },
   {
@@ skipping 286 matching lines @@
       "--compiler",
       "goma",
       "--goma-jsonstatus",
       "/path/to/tmp/json",
       "--goma-service-account-json-file",
       "C:\\creds\\service_accounts\\service-account-goma-client.json",
       "--goma-dir",
       "[CACHE]\\cipd\\goma",
       "--",
       "browser_tests",
-      "chromium_builder_webrtc",
       "content_browsertests",
       "content_unittests",
       "media_unittests",
       "remoting_unittests"
     ],
     "env": {
       "GOMA_SERVICE_ACCOUNT_JSON_FILE": "C:\\creds\\service_accounts\\service-account-goma-client.json"
     },
     "name": "compile",
     "~followup_annotations": [
@@ skipping 77 matching lines @@
     "~followup_annotations": [
       "@@@STEP_TEXT@Win10 Tester<br />Win7 Tester@@@"
     ]
   },
   {
     "name": "$result",
     "recipe_result": null,
     "status_code": 0
   }
 ]