This CL attempts to annotate accesses on >16 API levels using as small scopes as possible. The TargetApi notations mean "yes, I know I'm accessing a higher API and I take responsibility for gating the call on Android API level". The Encoder/Decoder classes are annotated on the whole class, but they're only accessed through JNI; we should annotate on method level otherwise and preferably on private methods. This patch also fixes some compiler-level deprecation warnings (i.e. -Xlint:deprecation), but probably not all of them. BUG=webrtc:5063 R=henrika@webrtc.org, kjellander@webrtc.org, magjed@webrtc.org Review URL: https://codereview.webrtc.org/1412673008 . Cr-Commit-Position: refs/heads/master@{#10624}