Revert of Simplify form validation handling

Revert of Simplify form validation handling (patchset #1 id:20001 of https://codereview.chromium.org/943303002/)

Reason for revert:
This CL breaks browser test:
AllForms_FormStructureBrowserTest.DataDrivenHeuristics_108

http://build.chromium.org/p/chromium.webkit/builders/Mac10.8%20Tests/builds/12230
http://build.chromium.org/p/chromium.webkit/builders/Linux%20Tests/builds/42755
http://build.chromium.org/p/chromium.webkit/builders/Linux%20ChromiumOS%20Tests%20%281%29/builds/10647
http://build.chromium.org/p/chromium.webkit/builders/Linux%20ChromiumOS%20Tests%20%28dbg%29%281%29/builds/6767

Bisected locally on Linux:
./out/Release/browser_tests  --gtest_filter=AllForms/FormStructureBrowserTest.DataDrivenHeuristics/108

Blink 190722 / Chromium 317759: OK
Blink 190723 / Chromium 317759: NG

So Blink 190723 is reverted.

Original issue's description:
> Simplify form validation handling
> 
> This CL contains some part of https://codereview.chromium.org/460343004/ by
> sudarshan.p, which was reverted by a performance regression.
> 
> This CL simplifies form validation state handling code by
>  - lazy update of m_isValid
>    setNeedsValidityCheck just makes m_isValid dirty.
>  - m_isValid takes care of willValidate state too.
>    m_isValid = !willValidate() || valid()
> 
> We switched to invalidation sets for :valid and :invalid by Blink
> r184392. Calling pseudoStateChanged() for unchanged validity state won't have so
> bad performance. So, we can evaluate m_isValid lazily.
> 
> We need to change the meaning of m_isValid slightly so that it takes care of
> willValidate(). This is necessary to clean m_validityIsDirty of associated
> controls in HTMLFormElement::checkInvalidControlsAndCollectUnhandled.
> Without this change, there would be a case where willValidate state
> change won't invalidate :valid :invalid style of <form>.
> 
> This CL will have a few percent regression on blink_perf.dom:textarea-edit.
> A fix for the performance regression will be landed soon.
> 
> BUG=
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=190723

TBR=keishi@chromium.org,tkent@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=190744

[hiroshige, 2015-02-24 11:27:04]

Created Revert of Simplify form validation handling

[commit-bot: I haz the power, 2015-02-24 11:27:50]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/948373002/1

[commit-bot: I haz the power, 2015-02-24 11:28:31]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=190744

[tkent, 2015-02-24 22:00:14]

lgtm.  thank you for gardening.