Update src/svg to follow C++11 style rule for {virtual,override}.

Update src/svg to follow C++11 style rule for {virtual,override}.

The Google style guide states that only one of {virtual,override,final}
should be used for each declaration, since override implies virtual
and final implies both virtual and override.

The entries were found using the following command line:

$ find src/ -iname "*.h" -o -iname "*.cpp" | xargs pcregrep -M
"[^\n/]+virtual\ [^;{]+\ [a-zA-Z0-9_]+\([^;{]+\ override[ \n]*[;{]"

The regex was a courtesy of nick@chromium.org

BUG=None
R=mtklein@google.com

Committed: https://skia.googlesource.com/skia/+/8566539f980ceb32673b843b94acd9e534f06676

[tfarina, 2015-05-03 21:55:11]

The CQ bit was checked by tfarina@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2015-05-03 21:55:14]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1123573004/1

[commit-bot: I haz the power, 2015-05-03 21:58:05]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-05-03 21:58:07]

Dry run: This issue passed the CQ dry run.

[mtklein, 2015-05-04 13:40:08]

The CQ bit was checked by mtklein@google.com

[mtklein, 2015-05-04 13:40:09]

lgtm

[commit-bot: I haz the power, 2015-05-04 13:40:18]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1123573004/1

[commit-bot: I haz the power, 2015-05-04 13:40:38]

Committed patchset #1 (id:1) as
https://skia.googlesource.com/skia/+/8566539f980ceb32673b843b94acd9e534f06676