Update bindings classes to use OVERRIDE / FINAL when needed

Update bindings classes to use OVERRIDE / FINAL when needed

Update bindings classes to use OVERRIDE / FINAL when needed. Those are useful for
error checking or performance when the compiler supports it.

R=esprehn, abarth, haraken
BUG=None

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=164739

[haraken, 2014-01-08 22:58:05]

LGTM

[commit-bot: I haz the power, 2014-01-08 23:51:02]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/ch.dumez@samsung.com/128973003/1

[commit-bot: I haz the power, 2014-01-09 04:04:51]

Change committed as 164739

[marja, 2014-01-09 14:25:06]

Curious: what's the perf benefit of OVERRIDE or FINAL? I know there's the error
checking aspect (looking forward to OVERRIDE checking being enabled for Blink!),
but the perf aspect is unclear to me.

[Inactive, 2014-01-09 14:36:17]

On 2014/01/09 14:25:06, marja wrote:
> Curious: what's the perf benefit of OVERRIDE or FINAL? I know there's the
error
> checking aspect (looking forward to OVERRIDE checking being enabled for
Blink!),
> but the perf aspect is unclear to me.

OVERRIDE has no impact on perf, it is merely useful for error checking.

However, FINAL can have an impact on perf because:
- Some virtual calls can be resolved at compile time (when the virtual method is
marked as FINAL for the class of the current object instance). We therefore
avoid  the overhead of checking the vtable in this case.
- It allows the compiler to inline some virtual function calls in cases it could
not before (related to the previous point)

Note that we currently don't build with c++11 support with gcc. Therefore, for
now, this matters only for clang builds (I believe thakis enabled C++11 for
clang builds).

[marja, 2014-01-09 15:21:55]

k, good to know, thx.