Improve performance of HTMLSelectElement::m_listItems update.

Improve performance of HTMLSelectElement::m_listItems update.

This CL introduces a fast path to update m_listItems directly instead of throwing
it away and reconstructing it. The fast path supports:
 - Prepend an OPTION to a SELECT element
 - Append an OPTION to a SELECT element
 - Remove an OPTION child from a SELECT element or an OPTGROUP element.

Removing 20,000 OPTIONs: 2,813ms -> 200ms

BUG=620142, 624220
Committed: https://crrev.com/ef9c38f033c0f5b11defe2210d2d00737c41b76e
Cr-Commit-Position: refs/heads/master@{#403093}

[tkent, 2016-06-30 01:31:58]

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

[tkent, 2016-06-30 01:31:58]

Keishi, would you review this please?

[keishi, 2016-06-30 01:43:18]

LGTM

[tkent, 2016-06-30 01:47:34]

The CQ bit was checked by tkent@chromium.org

[commit-bot: I haz the power, 2016-06-30 01:48:01]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-06-30 02:29:34]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2016-06-30 02:29:34]

Try jobs failed on following builders:
  linux_chromium_chromeos_ozone_rel_ng on master.tryserver.chromium.linux
(JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_...)

[tkent, 2016-06-30 02:30:07]

The CQ bit was checked by tkent@chromium.org

[commit-bot: I haz the power, 2016-06-30 02:30:29]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-06-30 03:34:14]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2016-06-30 03:34:15]

Try jobs failed on following builders:
  linux_chromium_chromeos_ozone_rel_ng on master.tryserver.chromium.linux
(JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_...)

[tkent, 2016-06-30 03:35:18]

The CQ bit was checked by tkent@chromium.org

[commit-bot: I haz the power, 2016-06-30 03:35:42]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[tkent, 2016-06-30 04:06:57]

The CQ bit was unchecked by tkent@chromium.org

[tkent, 2016-06-30 04:08:03]

The CQ bit was checked by tkent@chromium.org

[tkent, 2016-06-30 04:08:04]

The patchset sent to the CQ was uploaded after l-g-t-m from keishi@chromium.org
Link to the patchset: https://codereview.chromium.org/2110303002/#ps20001
(title: "Avoid DCHECK failure in OOBE tests")

[commit-bot: I haz the power, 2016-06-30 04:08:17]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-06-30 05:27:10]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2016-06-30 05:28:33]

Description was changed from

==========
Improve performance of HTMLSelectElement::m_listItems update.

This CL introduces a fast path to update m_listItems directly instead of
throwing
it away and reconstructing it. The fast path supports:
 - Prepend an OPTION to a SELECT element
 - Append an OPTION to a SELECT element
 - Remove an OPTION child from a SELECT element or an OPTGROUP element.

Removing 20,000 OPTIONs: 2,813ms -> 200ms

BUG=620142, 624220
==========

to

==========
Improve performance of HTMLSelectElement::m_listItems update.

This CL introduces a fast path to update m_listItems directly instead of
throwing
it away and reconstructing it. The fast path supports:
 - Prepend an OPTION to a SELECT element
 - Append an OPTION to a SELECT element
 - Remove an OPTION child from a SELECT element or an OPTGROUP element.

Removing 20,000 OPTIONs: 2,813ms -> 200ms

BUG=620142, 624220

Committed: https://crrev.com/ef9c38f033c0f5b11defe2210d2d00737c41b76e
Cr-Commit-Position: refs/heads/master@{#403093}
==========

[commit-bot: I haz the power, 2016-06-30 05:28:34]

Patchset 2 (id:??) landed as
https://crrev.com/ef9c38f033c0f5b11defe2210d2d00737c41b76e
Cr-Commit-Position: refs/heads/master@{#403093}