Add WebElement::isEditable.

Add WebElement::isEditable.

This will replace RenderViewImpl::IsEditableNode, and fixes
bugs where for example a <fieldset disabled> would not be
accounted for. It also adds tests for this API.

R=dglazkov@chromium.org

Committed: https://crrev.com/8891dc44eda41de9755e2ef86f64b3a9d28b5a9a
git-svn-id: svn://svn.chromium.org/blink/trunk@202307 bbb929c8-8fbe-4397-9dbb-9b2b20218538

[esprehn, 2015-09-15 23:50:56]

esprehn@chromium.org changed reviewers:
+ ojan@chromium.org

[esprehn, 2015-09-15 23:50:59]

The CQ bit was checked by esprehn@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2015-09-15 23:51:13]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1347893002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1347893002/1

[dglazkov, 2015-09-15 23:51:53]

lgtm

[esprehn, 2015-09-16 00:15:58]

The CQ bit was unchecked by esprehn@chromium.org

[esprehn, 2015-09-16 00:15:59]

The CQ bit was checked by esprehn@chromium.org

[commit-bot: I haz the power, 2015-09-16 00:16:42]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1347893002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1347893002/1

[commit-bot: I haz the power, 2015-09-16 01:32:44]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=202307

[commit-bot: I haz the power, 2015-09-23 12:52:33]

Patchset 1 (id:??) landed as
https://crrev.com/8891dc44eda41de9755e2ef86f64b3a9d28b5a9a