media/gpu/vaapi/VaapiWrapper: Add kVpp mode and get rid of vpp specific variables

VaapiWrapper does initializetion for VPP (Video Post Processing) in the same
VaapiWrapper instance that is created for kDecode. VaapiWrapper thus has
VAConfigID, VAContextID, VABufferID especially for VPP. We would rather process
VPP in another VaapiWrapper. kVpp mode is added for this purpose.

Bug: 898423
Test: VDA unittest on eve
Change-Id: I35d4198dc6285d356987b4b4b6e4f90bd5e59cd1
Reviewed-on: https://chromium-review.googlesource.com/c/1348869
Commit-Queue: Hirokazu Honda <hiroh@chromium.org>
Reviewed-by: Miguel Casas <mcasas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#618106}
8 files changed