Revert of Prevent inherited style from propagating into a plugin placeholder.

Revert of Prevent inherited style from propagating into a plugin placeholder. (patchset #3 id:40001 of https://codereview.chromium.org/669883003/)

Reason for revert:
Causing layout test fast/plugins/plugin-placeholder-inherit.html to fail.

Original issue's description:
> Prevent inherited style from propagating into a plugin placeholder.
> 
> Without setting 'all: initial', it's possible for text colours and such to be
> inherited by the placeholder, which is unexpected.
> 
> TEST=fast/plugins/plugin-placeholder-inherit.html
> BUG=364716
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=184878

TBR=esprehn@chromium.org,mkwst@chromium.org,jbroman@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=364716
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=184880

[dcheng, 2014-11-05 19:21:42]

Created Revert of Prevent inherited style from propagating into a plugin
placeholder.

[commit-bot: I haz the power, 2014-11-05 19:22:45]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/706623003/1

[commit-bot: I haz the power, 2014-11-05 19:23:22]

Committed patchset #1 (id:1) as 184880