I420VideoFrame: Remove functions set_width and set_height

This is a partial reland of https://webrtc-codereview.appspot.com/39939004/.

The functions set_width and set_height in I420VideoFrame are not needed and just add complexity.

R=perkj@webrtc.org, tommi@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/41009004

Cr-Original-Commit-Position: refs/heads/master@{#8556}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: fd33293d58aa9e715000477dae3fdc0cfa394f42
6 files changed