The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/760c56deb503e184f25a77782e743b6d46732cb6

commit 760c56deb503e184f25a77782e743b6d46732cb6
Author: tkent <tkent@chromium.org>
Date: Fri Jul 01 06:28:36 2016

Update a comment and fix a possible crash in HTMLSelectElement::setRecalcListItems.

This is a follow-up of crrev.com/403093.

- Replace a TODO comment with an explanation, and add a test to reproduce the
  scenario.

- Fix a possible crash by m_listItems.remove(WTF::kNotFound) just in case.
  We don't find a reproduction.

BUG= 625050 

Review-Url: https://codereview.chromium.org/2103663006
Cr-Commit-Position: refs/heads/master@{#403416}

[modify] https://crrev.com/760c56deb503e184f25a77782e743b6d46732cb6/third_party/WebKit/Source/core/html/HTMLSelectElement.cpp
[modify] https://crrev.com/760c56deb503e184f25a77782e743b6d46732cb6/third_party/WebKit/Source/core/html/HTMLSelectElementTest.cpp

Your change meets the bar and is auto-approved for M53 (branch: 2785)

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/3fe2c3902b205e99caff0e774a1b4d19c019276d

commit 3fe2c3902b205e99caff0e774a1b4d19c019276d
Author: Kent Tamura <tkent@chromium.org>
Date: Fri Jul 01 22:30:55 2016

Merge "Update a comment and fix a possible crash in HTMLSelectElement::setRecalcListItems." to M53.

This is a follow-up of crrev.com/403093.

- Replace a TODO comment with an explanation, and add a test to reproduce the
  scenario.

- Fix a possible crash by m_listItems.remove(WTF::kNotFound) just in case.
  We don't find a reproduction.

BUG= 625050 ,625091

Review-Url: https://codereview.chromium.org/2103663006
Cr-Commit-Position: refs/heads/master@{#403416}
(cherry picked from commit 760c56deb503e184f25a77782e743b6d46732cb6)

Review URL: https://codereview.chromium.org/2118973003 .

Cr-Commit-Position: refs/branch-heads/2785@{#3}
Cr-Branched-From: 68623971be0cfc492a2cb0427d7f478e7b214c24-refs/heads/master@{#403382}

[modify] https://crrev.com/3fe2c3902b205e99caff0e774a1b4d19c019276d/third_party/WebKit/Source/core/html/HTMLSelectElement.cpp
[modify] https://crrev.com/3fe2c3902b205e99caff0e774a1b4d19c019276d/third_party/WebKit/Source/core/html/HTMLSelectElementTest.cpp

Issue 625091 has been merged into this issue.

Tested the issue on Win 7,Mac 10.11.5 and Ubuntu 14.04 using 53.0.2785.8 referring to the comment www. crbug.com/623891#c2 , and https://output.jsbin.com/fojaza.
The page shows unresponsive message while tried to delete 500000 and after clicked once or twice on "wait" option it deletes the options.If clicked on "Kill" the Aw,Snap! page is seen.

tkent@: Could you please review the attached screen shot and update if its fine.

Deleted: 625050_July_7.png 64.4 KB

	625050_July_7.png 64.4 KB View Download

#7, it's unrelated to this bug, and it's an expected behavior.

Thanks for the update, Adding the respective TE-Verified labels for the same.