Build HTMLFormElement::m_associatedElements lazily

Build HTMLFormElement::m_associatedElements lazily

HTMLFormElement::associate() and disassociate() don't update
m_associatedElements synchronously, and we build it by traversing a DOM tree on
demand.

The code becomes simpler and we don't need complex functions like
formElementIndexWithFormAttribute and formElementIndex any more.

Difference from r165846:
 Fixed a crash when a FORM with multiple elements magically associated by HTML parser is detach from the document. This contains a test for the crash.

BUG=334556, 338764
TEST=none; no user-visible behavior changes.

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=166029

[tkent, 2014-01-27 09:10:32]

Keishi, would you review this please?

[keishi, 2014-01-27 10:57:46]

lgtm

[commit-bot: I haz the power, 2014-01-27 11:16:37]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/tkent@chromium.org/145353004/1

[commit-bot: I haz the power, 2014-01-27 11:20:42]

Change committed as 165846

[gavinp, 2014-01-28 18:37:06]

On 2014/01/27 11:20:42, I haz the power (commit-bot) wrote:
> Change committed as 165846

Reverted, as it was suspected in
https://code.google.com/p/chromium/issues/detail?id=338764&thanks=338764&ts=1...
.

[tkent, 2014-01-29 01:02:15]

https://codereview.chromium.org/145353004/diff/1/Source/core/html/HTMLFormEle...
File Source/core/html/HTMLFormElement.cpp (right):

https://codereview.chromium.org/145353004/diff/1/Source/core/html/HTMLFormEle...
Source/core/html/HTMLFormElement.cpp:140:
notifyFormRemovedFromTree(associatedElements(), root);
We need to pass a copy of associatedElement(). Unless it, formRemovedFromTree
can clears associatedElements.

[commit-bot: I haz the power, 2014-01-29 02:30:55]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/tkent@chromium.org/145353004/100001

[commit-bot: I haz the power, 2014-01-29 09:30:51]

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

[commit-bot: I haz the power, 2014-01-29 09:32:28]

CQ bit was unchecked on CL. Ignoring.

[commit-bot: I haz the power, 2014-01-29 09:55:14]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/tkent@chromium.org/145353004/100001

[commit-bot: I haz the power, 2014-01-29 13:17:34]

CQ bit was unchecked on CL. Ignoring.

[commit-bot: I haz the power, 2014-01-29 13:19:06]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/tkent@chromium.org/145353004/100001

[commit-bot: I haz the power, 2014-01-29 16:20:17]

Change committed as 166029

[commit-bot: I haz the power, 2014-01-29 16:20:37]

CQ bit was unchecked on CL. Ignoring.