Remove an old constructor from WebNotificationData, add a layout test.

Remove an old constructor from WebNotificationData, add a layout test.

Now that the users in Chromium pass the "silent" flag as well, we can
remove the old constructor.

This patch also introduces a test to verify that the "silent" attribute
will be properly reflected in the Notification object received in the
"notificationclick" event, as well as reflection in a newly created
Notification object through the constructor.

This is part of a three-sided patch:
  [1] https://codereview.chromium.org/960163003/
  [2] https://codereview.chromium.org/965573002/
  [3] This patch.

BUG=442134
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=191705

[Peter Beverloo, 2015-02-26 23:08:12]

peter@chromium.org changed reviewers:
+ mvanouwerkerk@chromium.org

[Peter Beverloo, 2015-02-26 23:08:13]

+mvanouwerkerk for review

[Michael van Ouwerkerk, 2015-02-27 11:31:32]

lgtm

[Peter Beverloo, 2015-03-02 18:49:53]

Michael, can you please review the layout test changes I just added to this
patch?

[Michael van Ouwerkerk, 2015-03-03 12:28:29]

also lgtm

[Peter Beverloo, 2015-03-11 11:33:28]

The CQ bit was checked by peter@chromium.org

[Peter Beverloo, 2015-03-11 11:33:29]

The patchset sent to the CQ was uploaded after l-g-t-m from
mvanouwerkerk@chromium.org
Link to the patchset: https://codereview.chromium.org/965463003/#ps80001 (title:
" ")

[commit-bot: I haz the power, 2015-03-11 11:33:37]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/965463003/80001

[commit-bot: I haz the power, 2015-03-11 14:22:21]

Committed patchset #5 (id:80001) as
https://src.chromium.org/viewvc/blink?view=rev&revision=191705