GitLab

Add const to members that are set in the ctor and never change. Also
remove the unused status field from PageFlipRequest.

Bug: none
Test: compile
Change-Id: I8bc54acd67812d860a87fab64381c7ae0f6b7b24
Reviewed-on: https://chromium-review.googlesource.com/1234223Reviewed-by: Daniel Nicoara <dnicoara@chromium.org>
Commit-Queue: Michael Spang <spang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#592543}