Blender Git Loki

Sequencer: Do not redraw during playback.

When using large sequences including audio the drawing of the audio on
top of the strip takes a lot of time. This effects the playback
performance heavily.

During the animation playback performance there was a solution for this
by only drawing the playhead overlay. This was reverted for the sequence
editor as it didn't update the color strips when they were animated.

This patch checks if there are animated color strips if so the full
screen is redrawn, otherwise only the playhead is redrawn.

Reviewed By: ISS

Differential Revision: https://developer.blender.org/D11580