Revert 181400 "Partial revert of r178392"

> Partial revert of r178392
>
> An unnecessary modification that was made in Blink r178392 was causing
> a regression in the rendering of the inspector timeline.  Pulling it
> out
>
> BUG=408080
> R=kbr@chromium.org
>
> Review URL: https://codereview.chromium.org/541783002

TBR=junov@chromium.org
BUG=

Review URL: https://codereview.chromium.org/542963002

git-svn-id: svn://svn.chromium.org/blink/trunk@181433 bbb929c8-8fbe-4397-9dbb-9b2b20218538