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Switch to use Win32 CONDITION_VARIABLE like the rest of Chromium.

This greatly simplifies the implementation of ThreadCondition
class for Windows with better performance.

Change-Id: If4d007ddf4c8f115c0f5363dc234d220d2fe9ee8
Reviewed-on: https://chromium-review.googlesource.com/670200Reviewed-by: Kent Tamura <tkent@chromium.org>
Commit-Queue: Kent Tamura <tkent@chromium.org>
Cr-Commit-Position: refs/heads/master@{#502801}