Correctly define OVERRIDE / FINAL when building with g++ 4.7 and C++11 support

Correctly define OVERRIDE / FINAL when building with g++ 4.7 and C++11 support

g++ 4.7 and later support explicit virtual overrides when building with C++11 support
enabled. Blink correctly detects that and defines OVERRIDE / FINAL properly. However,
Chrome does not detect compiler support properly and makes OVERRIDE / FINAL no-ops.

This causes the compiler to complain about OVERRIDE / FINAL being redefined.
This CL updates base/compiler_specific.h to define OVERRIDE / FINAL properly when
g++ 4.7 is used with C++11 support enabled.

See this page for GCC support of C++11 features:
http://gcc.gnu.org/projects/cxx0x.html

BUG=233330
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=239207

[Inactive, 2013-12-05 20:38:11]

FYI, the exact same issue exists in webrtc and libjingle.

[Nico, 2013-12-05 20:40:26]

We don't build with C++11 mode when building with gcc though, right?

[Nico, 2013-12-05 20:41:14]

But sure, lgtm

[Inactive, 2013-12-05 20:54:10]

On 2013/12/05 20:40:26, Nico wrote:
> We don't build with C++11 mode when building with gcc though, right?

Right, we don't build with C++11 support enabled when using gcc at the moment.
We do with clang though so I'd like the gcc build to catch up.

[commit-bot: I haz the power, 2013-12-05 21:38:35]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/ch.dumez@samsung.com/107113002/1

[commit-bot: I haz the power, 2013-12-06 07:43:45]

Retried try job too often on linux_rel for step(s) browser_tests
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=linux_rel&...

[commit-bot: I haz the power, 2013-12-06 14:08:33]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/ch.dumez@samsung.com/107113002/1

[commit-bot: I haz the power, 2013-12-06 14:16:27]

Change committed as 239207