Add three UseCounters for LABEL element.

Add three UseCounters for LABEL element.

HTMLLabelElementFormIsDifferentFromControlForm:
HTMLLabelElementHasNoControlAndFormIsAncestor:
  They are for label[form] deprecation.
  https://github.com/whatwg/html/issues/787

HTMLLabelElementControlForNonFormAssociatedElement
  This is for a LABEL with PROGRESS or METER.
  This is counted on any LABEL-specific behaviors.
  e.g.  |form| IDL access, |control| IDL access, Clicking a LABEL, etc.

This CL has no user-visible behavior changes.

BUG=594447
TBR=isherman@chromium.org

Review URL: https://codereview.chromium.org/1790143004

Cr-Commit-Position: refs/heads/master@{#380933}
(cherry picked from commit 39e402647a842f4fcc12faded11d486aca8eda47)

Committed: https://chromium.googlesource.com/chromium/src/+/e1c470bb537ac2c1fe83e8c1f6b3719782033ed9

[tkent, 2016-03-15 07:58:00]

Description was changed from

==========
Add three UseCounters for LABEL element.

HTMLLabelElementFormIsDifferentFromControlForm:
HTMLLabelElementHasNoControlAndFormIsAncestor:
  They are for label[form] deprecation.
  https://github.com/whatwg/html/issues/787

HTMLLabelElementControlForNonFormAssociatedElement
  This is for a LABEL with PROGRESS or METER.
  This is counted on any LABEL-specific behaviors.
  e.g.  |form| IDL access, |control| IDL access, Clicking a LABEL, etc.

This CL has no user-visible behavior changes.

BUG=594447
TBR=isherman@chromium.org

Review URL: https://codereview.chromium.org/1790143004

Cr-Commit-Position: refs/heads/master@{#380933}
(cherry picked from commit 39e402647a842f4fcc12faded11d486aca8eda47)
==========

to

==========
Add three UseCounters for LABEL element.

HTMLLabelElementFormIsDifferentFromControlForm:
HTMLLabelElementHasNoControlAndFormIsAncestor:
  They are for label[form] deprecation.
  https://github.com/whatwg/html/issues/787

HTMLLabelElementControlForNonFormAssociatedElement
  This is for a LABEL with PROGRESS or METER.
  This is counted on any LABEL-specific behaviors.
  e.g.  |form| IDL access, |control| IDL access, Clicking a LABEL, etc.

This CL has no user-visible behavior changes.

BUG=594447
TBR=isherman@chromium.org

Review URL: https://codereview.chromium.org/1790143004

Cr-Commit-Position: refs/heads/master@{#380933}
(cherry picked from commit 39e402647a842f4fcc12faded11d486aca8eda47)

Committed:
https://chromium.googlesource.com/chromium/src/+/e1c470bb537ac2c1fe83e8c1f6b3...
==========

[tkent, 2016-03-15 07:58:07]

Committed patchset #1 (id:1) manually as
e1c470bb537ac2c1fe83e8c1f6b3719782033ed9.