Update {virtual,override} to follow C++11 style in src/pipe.

Update {virtual,override} to follow C++11 style in src/pipe.

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/pipe -iname "*.h" -or -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/+/d96fd0c073fa44a475363003c8f0d25a077edc6c

[mtklein, 2015-04-24 19:44:55]

Ah, great!  As you might have guessed, we fixed all the single-line
virtual...override cases, but I didn't know how to write a regex to span
multiple lines.

lgtm

[tfarina, 2015-04-24 20:07:08]

The CQ bit was checked by tfarina@chromium.org

[commit-bot: I haz the power, 2015-04-24 20:07:17]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1104863003/1

[commit-bot: I haz the power, 2015-04-24 20:12:48]

Committed patchset #1 (id:1) as
https://skia.googlesource.com/skia/+/d96fd0c073fa44a475363003c8f0d25a077edc6c