Layout Tests: Remove assert_will_be_idl_attribute() helper

Layout Tests: Remove assert_will_be_idl_attribute() helper

Now that DOM attributes are on prototype chains, just use
assert_idl_attribute().

BUG=43394
Committed: https://crrev.com/b832a84ce777bc4ea348c2e1eba7844e83f5bd8c
Cr-Commit-Position: refs/heads/master@{#391046}

[jsbell, 2016-04-29 19:09:16]

jsbell@chromium.org changed reviewers:
+ jkarlin@chromium.org, mek@chromium.org

[jsbell, 2016-04-29 19:09:17]

mek@, jkarlin@ - please take a look?

The SyncEvent's assertion was incorrect. I think I captured the correct
semantics? And added a case for `lastChance` while I was there.

[jkarlin, 2016-05-02 15:43:43]

background_sync/ lgtm. Thanks!

[Marijn Kruisselbrink, 2016-05-02 17:33:05]

lgtm

[jsbell, 2016-05-02 17:37:18]

The CQ bit was checked by jsbell@chromium.org

[commit-bot: I haz the power, 2016-05-02 17:37:47]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1936533003/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1936533003/20001

[commit-bot: I haz the power, 2016-05-02 20:36:12]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2016-05-02 20:38:39]

Description was changed from

==========
Layout Tests: Remove assert_will_be_idl_attribute() helper

Now that DOM attributes are on prototype chains, just use
assert_idl_attribute().

BUG=43394
==========

to

==========
Layout Tests: Remove assert_will_be_idl_attribute() helper

Now that DOM attributes are on prototype chains, just use
assert_idl_attribute().

BUG=43394

Committed: https://crrev.com/b832a84ce777bc4ea348c2e1eba7844e83f5bd8c
Cr-Commit-Position: refs/heads/master@{#391046}
==========

[commit-bot: I haz the power, 2016-05-02 20:38:40]

Patchset 2 (id:??) landed as
https://crrev.com/b832a84ce777bc4ea348c2e1eba7844e83f5bd8c
Cr-Commit-Position: refs/heads/master@{#391046}