pkg/front_end/testcases/dart2js/tear_off_patch/libraries.json

{
  "dart2js": {
    "comment:0": "This adds to the default libraries found in the platform.",
    "libraries": {
      "test": {
        "patches": [
          "patch_lib.dart"
        ],
        "uri": "origin_lib.dart"
      }
    }
  }
}