Revert 151879 "Remove virtual from functions that are never over..."

Revert 151879 "Remove virtual from functions that are never over..."

Broke two Chromium tests

BUG=247325
> 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
> 
> Review URL: https://chromiumcodereview.appspot.com/16465002

TBR=dmazzoni@chromium.org

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=151938

[dmazzoni, 2013-06-06 15:26:59]

Committed patchset #1 manually as r151938.