HTMLOptionElement::defaultSelected should affect selection state of other option elements.

According to the standard, we should set selectedness to true if defaultSelected
is set to true, and we should not set selectedness to false if defaultSelected
is set to false because the standard says nothing about it.

[1]
> Whenever an option element's selected attribute is added, its selectedness
> must be set to true.

When the selectedness of an option is udpated, other options's selectedness
should become false.

[2]
> If the multiple attribute is absent, whenever an option element in the select
> element's list of options has its selectedness set to true, and whenever an
> option element with its selectedness set to true is added to the select
> element's list of options, the user agent must set the selectedness of all the
> other option elements in its list of options to false.

The old behavior doesn't match to the standard and any other browsers.
The new behavior matches to IE10 and the standard.

We need to update pseudoclass-update-checked-option.html because the
expected behavior of the test was incorrect.

[1] http://www.whatwg.org/specs/web-apps/current-work/multipage/the-button-element.html#attr-option-selected
[2] http://www.whatwg.org/specs/web-apps/current-work/multipage/the-button-element.html#the-select-element

BUG=260141

Review URL: https://chromiumcodereview.appspot.com/19547011

git-svn-id: svn://svn.chromium.org/blink/trunk@154612 bbb929c8-8fbe-4397-9dbb-9b2b20218538