Merge "Clarify start/stop DTMF tone API documentation." am: b212a4bfc7 am: def39f477a am: 20803ecd8f

Original change: https://android-review.googlesource.com/c/platform/frameworks/base/+/2423245

Change-Id: I26ef42b3709b0f52007b4aac41121009d0635ab1
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>