Revert of Allow default font size changing on Linux.

Revert of Allow default font size changing on Linux. (patchset #10 id:180001 of https://codereview.chromium.org/549303004/ )

Reason for revert:
This caused a regression:
https://code.google.com/p/chromium/issues/detail?id=525176

Original issue's description:
> Allow default font size changing on Linux.
>
> Currently base rendering font size on Linux is hardcoded to 16.0 with no possibility of changing it. This patch add such possibility in RendererPreferences.
>
> Webkit part: https://codereview.chromium.org/570243002/
>
> BUG=
>
> Committed: https://crrev.com/f0bc1a926d8f0326ef38b8374e42bc8e244dd2ba
> Cr-Commit-Position: refs/heads/master@{#344746}

TBR=jochen@chromium.org,erg@chromium.org,eseidel@chromium.org,jln@chromium.org,dmazzoni@chromium.org,plundblad@chromium.org,joleksy@opera.com
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=

Committed: https://crrev.com/3b1be63348b61357f9dd1905f8a012fdf10bd523
Cr-Commit-Position: refs/heads/master@{#345852}

[kochi, 2015-08-27 11:57:47]

Created Revert of Allow default font size changing on Linux.

[commit-bot: I haz the power, 2015-08-27 11:58:10]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1319613004/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1319613004/1

[commit-bot: I haz the power, 2015-08-27 11:58:58]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-08-27 11:59:35]

Patchset 1 (id:??) landed as
https://crrev.com/3b1be63348b61357f9dd1905f8a012fdf10bd523
Cr-Commit-Position: refs/heads/master@{#345852}