viz: Remove dead code after turning on presentation feedback.

After presentation-feedback is turned on by default for every frame in
crrev.com/591777, the following fields are no longer needed:
 . SwapBuffersFlag for presentation-feedback.
 . OutputSurfaceFrame::need_presentation_feedback.

The change to turn on the presentation-feedback every frame has been
in stable without issues. So remove the dead code no longer needed.

TBR=danakj@: mechanical changes in cc/ and content/browser/compositor
BUG=883592

Change-Id: Id4bbb3bae17c5e808095f6d2aecca0e66b295e3c
Reviewed-on: https://chromium-review.googlesource.com/c/1232513
Commit-Queue: Sadrul Chowdhury <sadrul@chromium.org>
Reviewed-by: Jonathan Backer <backer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#616588}
36 files changed