Upgrade emulator to emu-master-dev build 6278574 am: 9c1912d89f am: c7d2d06358 am: 0815c818c8

Original change: https://googleplex-android-review.googlesource.com/c/platform/prebuilts/android-emulator/+/10610251

Change-Id: Ia349e398d3f032b61709598acb1bd687bb4ecb81