Reland "Show controls and update time indicators during seeking" (again)

This reverts commit 57d8bde6a48a121cbf7dc91c08b4c4a8ffaf712c.

Original commit message:
> Show controls and update time indicators during seeking
>
> This commit modifies the MediaControls to show the controls and update
> the current time indicators (current time text + timeline thumb)
> immediately during seek requests so the element behavior during rapid
> seek requests (e.g. user is holding down the FF button on their BT
> keyboard) look similar to when a user is scrubbing the timeline with
> their mouse.
>
> Bug: 748749
>
> TEST=MediaControlsImplTest, manual testing
>      out/Debug/bin/run_webkit_unit_tests -f *MediaControlsImplTest*
>
> Change-Id: I6588aded2a93e081a6ca638ee1da534ea00abf4d
> Reviewed-on: https://chromium-review.googlesource.com/c/1274945
> Commit-Queue: Tommy Steimel <[email protected]>
> Reviewed-by: Mounir Lamouri <[email protected]>
> Reviewed-by: Tommy Steimel <[email protected]>
> Cr-Commit-Position: refs/heads/master@{#636493}

This commit was reverted for causing a layout test
(controls-drag-timebar-rendering.html) to be flaky.

After close examination, it was determined that this layout test was
verifying some functionality that no longer exists, and was
previously passing erroneously. In relanding this commit, that test
has been deleted.

Bug: 937029
Change-Id: I012f767f4a0d072509a7feff199eb6135959534c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1558193
Reviewed-by: Tommy Steimel <[email protected]>
Reviewed-by: Mounir Lamouri <[email protected]>
Commit-Queue: Mounir Lamouri <[email protected]>
Cr-Commit-Position: refs/heads/master@{#649106}
10 files changed