Use a better c++11 readiness check.

Use a better c++11 readiness check.

This is like https://codereview.chromium.org/443483002/ , but that check wasn't
as convincing as it could have been since clang accepts override and final as
an extension in c++98 mode. No intended behavior change.

If your bot can't deal with this, please let me know!

BUG=none
R=viettrungluu@chromium.org

Committed: https://chromium.googlesource.com/chromium/src/+/83ea589954286349dfb86cbfb0c9337ae5019108

[Nico, 2014-09-16 18:34:35]

thakis@chromium.org changed reviewers:
+ ajwong@chromium.org

[Nico, 2014-09-16 18:34:36]

(I checked that clang rejects static_assert without -std=gnu++11. The old check
wasn't useless, as it found older gccs at least.)

[viettrungluu, 2014-09-16 19:06:47]

viettrungluu@chromium.org changed reviewers:
+ viettrungluu@chromium.org

[viettrungluu, 2014-09-16 19:06:47]

lgtm

[commit-bot: I haz the power, 2014-09-16 19:45:05]

Patchset 1 (id:??) landed as
https://crrev.com/83ea589954286349dfb86cbfb0c9337ae5019108
Cr-Commit-Position: refs/heads/master@{#295128}

[Nico, 2014-09-16 19:45:31]

Committed patchset #1 (id:1) manually as 83ea589 (presubmit successful).