Revert of Oilpan: Trace CSSFontFaceSrcValue::m_svgFontFaceElement.

Revert of Oilpan: Trace CSSFontFaceSrcValue::m_svgFontFaceElement. (https://codereview.chromium.org/333403004/)

Reason for revert:
This patch leaks svg-font-face-leak-document test

http://test-results.appspot.com/dashboards/flakiness_dashboard.html#group=%40ToT%20Blink&tests=svg/svg-font-face-leak-document.html

Original issue's description:
> Oilpan: Trace CSSFontFaceSrcValue::m_svgFontFaceElement.
> 
> BUG=357163
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=176270

BUG=357163
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=176299

[kouhei (in TOK), 2014-06-17 07:38:34]

Created Revert of Oilpan: Trace CSSFontFaceSrcValue::m_svgFontFaceElement.

[kouhei (in TOK), 2014-06-17 07:39:23]

PTAL.

[Mads Ager (chromium), 2014-06-17 07:45:39]

LGTM, thanks Kouhei

[kouhei (in TOK), 2014-06-17 07:45:56]

The CQ bit was checked by kouhei@chromium.org

[kouhei (in TOK), 2014-06-17 07:46:10]

On 2014/06/17 07:45:39, Mads Ager (chromium) wrote:
> LGTM, thanks Kouhei

I'll work on a proper fix later.

[commit-bot: I haz the power, 2014-06-17 07:46:24]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/kouhei@chromium.org/337703004/1

[tkent, 2014-06-17 07:50:53]

lgtm.  Thanks!

[haraken, 2014-06-17 08:03:56]

LGTM

[commit-bot: I haz the power, 2014-06-17 08:51:22]

Change committed as 176299