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This is a reland of 0346a3a1
Original change's description:
> Adds predictable multimatch support in PreviewsOptimizationGuide
> 
> Supports multiple hint matches with precendence given to the match
> that occurs first in the configuration. Also, allows matches
> without whitelisted optimization to be able to turn off whitelisting
> for a host pattern (that otherwise would be whitelisted for another
> matching pattern that occurs later in config).
> 
> Bug: 783237
> Change-Id: I9239b74b170a1d5a19b13caccecc732f9715de90
> Reviewed-on: https://chromium-review.googlesource.com/847816
> Reviewed-by: Ryan Sturm <ryansturm@chromium.org>
> Commit-Queue: Doug Arnett <dougarnett@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#526763}

Bug: 783237
Change-Id: I75cf52fbe3b471f81b3f18ae451d7daa0844190e
Reviewed-on: https://chromium-review.googlesource.com/849673
Commit-Queue: Doug Arnett <dougarnett@chromium.org>
Reviewed-by: Ryan Sturm <ryansturm@chromium.org>
Cr-Commit-Position: refs/heads/master@{#527094}