Revert "Remove hang watching of deprecated BrowserThreads."

This reverts commit 91c22dbfcbb85107b0a26c5952881aa904692611.

Reason for revert: https://bugs.chromium.org/p/chromium/issues/detail?id=768886#c34

I'm puzzled as to why but it seems removing hang watching of unused BrowserThreads causes a spike in hang reports of remaining watched threads...

Original change's description:
> Remove hang watching of deprecated BrowserThreads.
> 
> This is a partial reland of https://chromium-review.googlesource.com/c/chromium/src/+/705775
> 
> That CL caused issue 768886 (spike in hang reports). I suspect this
> was caused by a change in enum IDs rather than this change to the
> hang watching code and this CL will help narrow down the cause.
> 
> R=​asvitkine@chromium.org
> 
> NOPRESUBMIT=TRUE (shuffling of code using deprecated BrowserThread IDs)
> 
> Bug: 689520,768886
> Change-Id: Id7bf1c7b5f5d34c4b1e7b1e71e9b015725695997
> Reviewed-on: https://chromium-review.googlesource.com/743846
> Commit-Queue: Gabriel Charette <gab@chromium.org>
> Reviewed-by: Alexei Svitkine <asvitkine@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#512509}

TBR=gab@chromium.org,asvitkine@chromium.org
NOPRESUBMIT=TRUE

Skipping CQ checks because CL landed > 1 day ago.

Bug: 689520, 768886
Change-Id: I164eceed2a2354b3fa82d6ff73899417530aa3a5
Reviewed-on: https://chromium-review.googlesource.com/747661
Commit-Queue: Gabriel Charette <gab@chromium.org>
Reviewed-by: Gabriel Charette <gab@chromium.org>
Cr-Commit-Position: refs/heads/master@{#512907}
2 files changed