IDL compiler: simplify ExceptionState code in overloads

Slightly shorter by putting variable declaration+initialization at use,
rather than at top. This removes a extra branch and some complexity.

Followup to:
Generate a bit less code to handle failed arity checks.
https://codereview.chromium.org/105693002/
IDL compiler: sync Python to r163527
https://codereview.chromium.org/111793006/

BUG=270033

Review URL: https://codereview.chromium.org/110893005

git-svn-id: svn://svn.chromium.org/blink/trunk@163670 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Implement HTMLOptionElement.form as required by spec.

The spec tells us that an option element

  http://www.whatwg.org/specs/web-apps/current-work//#dom-option-form

only has a form value if inside a <select>. Implement this.

R=arv@chromium.org
BUG=324828
TEST=fast/forms/form-attribute

Review URL: https://codereview.chromium.org/102263006

git-svn-id: svn://svn.chromium.org/blink/trunk@163671 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Rollforward: Don't make autosizing containers for empty nodes.

This reverts https://src.chromium.org/viewvc/blink?view=revision&revision=163560.

BUG=

Review URL: https://codereview.chromium.org/99863005

git-svn-id: svn://svn.chromium.org/blink/trunk@163672 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Remove unused BaseDateAndTimeInputType::dateType.

BUG=

Review URL: https://codereview.chromium.org/112443002

git-svn-id: svn://svn.chromium.org/blink/trunk@163673 bbb929c8-8fbe-4397-9dbb-9b2b20218538