Merge "Add startCaptivePortalApp to system API" am: b53aeb4682 am: 1cd0e8f0fc am: 8020cb4517

Original change: https://android-review.googlesource.com/c/platform/frameworks/base/+/1639899

Change-Id: Ia3be29892f62b82d23a165bc8334a083c674aefb