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

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

Change-Id: I3fe36c88c02f281d63246007c2e004ebd75791f0
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>