WebRtcVideoEngine: Encapsulate logic for unifying internal and external video codecs

This CL encapsulates the logic for unifying the internal and external
video encoders into a helper class. The purpose is to prepare for
introducing a new video encoder factory interface that inherently
represents all encoders (i.e. both internal and external). A helper
interface EncoderFactoryAdapter is introduced that both the old
WebRtcVideoEncoderFactory and the new factory interface can implement
and serves as common point to leave the rest of the code unchanged.


Review-Url: https://codereview.webrtc.org/3006713002
Cr-Original-Commit-Position: refs/heads/master@{#19600}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: a35df4260f2e51f35e94fa74d1e840f73b597369
2 files changed