New SELECT Popup: Remove O(N^2) scan for OPTIONs.

New SELECT Popup: Remove O(N^2) scan for OPTIONs.

HTMLOptionElement::listIndex() is O(N), and we need to call it
for each of OPTIONs.
After this patch, PopupMenuImpl calculate listIndex incrementally
while iterating over OPTIONs.

This CL makes writeDocument() 16x faster with 43k OPTIONs.

BUG=500401
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=197429

[tkent, 2015-06-19 04:03:16]

tkent@chromium.org changed reviewers:
+ keishi@chromium.org

[tkent, 2015-06-19 04:03:16]

Keishi, would you review this please?

[keishi, 2015-06-19 04:06:43]

lgtm

[tkent, 2015-06-19 04:07:38]

The CQ bit was checked by tkent@chromium.org

[commit-bot: I haz the power, 2015-06-19 04:07:48]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1193793002/1

[commit-bot: I haz the power, 2015-06-19 04:11:55]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=197429