Revert "Remove throttled-progress updates flag"

This reverts commit 95f29fcd6f90903cbfbd71bbe6205d75cd55e915.

Reason for revert: Breaks tests on tablets: crbug.com/781789

Original change's description:
> Remove throttled-progress updates flag
> 
> This change removes the flag for the throttled progress bar, turning
> it on by default for all users.
> 
> BUG=759799
> 
> Change-Id: Ia15d5db65f27bab222d4aac9dadea24bccca0e23
> Reviewed-on: https://chromium-review.googlesource.com/726844
> Commit-Queue: Matthew Jones <[email protected]>
> Reviewed-by: Ted Choc <[email protected]>
> Cr-Commit-Position: refs/heads/master@{#513770}

[email protected],[email protected]

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 759799
Change-Id: I7b74c0cd824021c479661ea9f9466821fb4f98a6
Reviewed-on: https://chromium-review.googlesource.com/759113
Reviewed-by: Matthew Jones <[email protected]>
Commit-Queue: Matthew Jones <[email protected]>
Cr-Commit-Position: refs/heads/master@{#514992}
8 files changed