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These histograms were obsoleted recently.

I would like to bring them back to validate the hypothesis that the
HistoryQuickProvider / InMemoryURLIndex cache is not needed.

Details of experiment: go/chrome-omnibox-hqp-ablate-cache-file

Specifically, my theory is that the time it takes to restore + save the
cache file is in the same order of magnitude as it takes to rebuild the
index from the History DB.

The cache causes two known problems:
 1. Saving it is responsible for roughly 10% of shutdown hangs.
 2. Restoring it seems to take a lot of memory.

This CL is a partial revert of:
https://chromium-review.googlesource.com/c/chromium/src/+/2324551

Bug: 750845, 1032679, 1141539
Change-Id: I7e679c0ba602cf48ab10ad0a89bd75bc3dbf5ee6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2490148Reviewed-by: Mark Pearson <mpearson@chromium.org>
Commit-Queue: Tommy Li <tommycli@chromium.org>
Cr-Commit-Position: refs/heads/master@{#819950}