This CL changes YuvConverter to use an OpenGL Framebuffer as rendering target instead of an EGL pixel buffer surface. The purpose is to reduce the number of EGL contexts and to be able to use YuvConverter from EglRenderer without having to detach the EGL surface. BUG=webrtc:6470 Review-Url: https://codereview.webrtc.org/2436653003 Cr-Commit-Position: refs/heads/master@{#14699}