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This class is a successor to ThreadWatcher which aims to be more
versatile and provide a larger coverage for hang watching.

Bug: 1034046
Change-Id: I365fe8824eb34c37c75e6ddf6874ff26ecd494c6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2008189
Commit-Queue: Oliver Li <olivierli@chromium.org>
Reviewed-by: François Doray <fdoray@chromium.org>
Cr-Commit-Position: refs/heads/master@{#736080}