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This makes it possible to know what revision a graph corresponds to,
so that users know how old the graph they are viewing is and makes it
possible to track regressions.

Bug: 1115268
Change-Id: Iedceabe885d90b14bb639e810dcaa75f48be844a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2353292Reviewed-by: Mohamed Heikal <mheikal@chromium.org>
Commit-Queue: Henrique Nakashima <hnakashima@chromium.org>
Cr-Commit-Position: refs/heads/master@{#821836}