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Cleans up the Guts protocols from things that are no longer used.
Uses interfaceProvider everywhere instead of alternative accessors.

Bug: 1045659, 1045660
Change-Id: Ib3355505686c6b034e98373d380330dff256d8af
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2087675
Commit-Queue: Stepan Khapugin <stkhapugin@chromium.org>
Reviewed-by: Mark Cogan <marq@chromium.org>
Cr-Commit-Position: refs/heads/master@{#748190}