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Simply rename *_halv3 to *_delegate to keep git history.
Add an intermediate layer to prepare further refactor to support
multiple streams.

Bug: b:151047537
Test: Manually
Change-Id: Ic2db36b003206972aabd70a5ceafd00e9f8f1c3e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2351931
Commit-Queue: Heng-ruey Hsu <henryhsu@chromium.org>
Reviewed-by: Miguel Casas <mcasas@chromium.org>
Reviewed-by: Wei Lee <wtlee@chromium.org>
Auto-Submit: Heng-ruey Hsu <henryhsu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#834638}