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The thread cache is disabled on Windows, as TLS is not implemented
there. Add a Windows TLS implementation, and enable the thread cache.

Bug: 998048
Change-Id: Ia9d90d5d5e78611e00e6456a770bdf00f44bb773
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2426323
Commit-Queue: Benoit L <lizeb@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Cr-Commit-Position: refs/heads/master@{#816603}