Remove virtual from functions that are never overridden.

Remove virtual from functions that are never overridden.

I checked these by writing a quick Python script; none of these functions
are found in any other header files in this directory.

I was surprised how much this cuts down on code size. I'm going to
aggressively get rid of virtual functions when they're not useful.
The main reason this helps so much is because there are so many subclasses
of AccessibilityObject.

BUG=247082
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=151879

[aboxhall, 2013-06-05 18:58:42]

lgtm

[commit-bot: I haz the power, 2013-06-05 21:54:53]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/dmazzoni@chromium.org/16465002/1

[commit-bot: I haz the power, 2013-06-05 22:41:54]

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

[commit-bot: I haz the power, 2013-06-05 22:45:04]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/dmazzoni@chromium.org/16465002/1

[commit-bot: I haz the power, 2013-06-05 23:32:14]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/dmazzoni@chromium.org/16465002/1

[commit-bot: I haz the power, 2013-06-06 02:14:05]

Change committed as 151879