Merge "Support NetworkRequest.Builder with an existing request in shim" am: 230d5ae6b9 am: 78a2f05370 am: e8cc37823d

Original change: https://android-review.googlesource.com/c/platform/packages/modules/NetworkStack/+/1650233

Change-Id: I9e36a93d51101d3e2fa2e574c31fd9b05ff0e024