Update a test to use PushSubscription.getKey()

Update a test to use PushSubscription.getKey()

The PushSubscription.curve25519dh property is now exposed through a
getKey() method that takes the curve type as the first and only
argument. Update the test to use this instead.

This CL is part of a three-sided patch:
  [1] https://codereview.chromium.org/1309723004/
  [2] This CL.
  [3] https://codereview.chromium.org/1316693002/

BUG=486040
Committed: https://crrev.com/908a130993076bf98bb5db216bdec2a1919da88b
Cr-Commit-Position: refs/heads/master@{#345863}

[Peter Beverloo, 2015-08-25 13:19:57]

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

[Peter Beverloo, 2015-08-25 13:19:58]

PTAL

[Michael van Ouwerkerk, 2015-08-25 16:18:14]

lgtm

[Peter Beverloo, 2015-08-26 14:44:23]

The CQ bit was checked by peter@chromium.org

[commit-bot: I haz the power, 2015-08-26 14:45:03]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1314893002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1314893002/1

[commit-bot: I haz the power, 2015-08-26 15:02:35]

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

[commit-bot: I haz the power, 2015-08-26 15:02:35]

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

[Peter Beverloo, 2015-08-26 17:40:38]

The CQ bit was checked by peter@chromium.org

[commit-bot: I haz the power, 2015-08-26 17:41:33]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1314893002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1314893002/1

[commit-bot: I haz the power, 2015-08-26 17:54:12]

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

[commit-bot: I haz the power, 2015-08-26 17:54:13]

Try jobs failed on following builders:
  mac_chromium_rel_ng on tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/mac_chromium_rel_...)

[Peter Beverloo, 2015-08-27 11:35:02]

The CQ bit was checked by peter@chromium.org

[commit-bot: I haz the power, 2015-08-27 11:35:21]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1314893002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1314893002/1

[commit-bot: I haz the power, 2015-08-27 13:32:21]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-08-27 13:33:34]

Patchset 1 (id:??) landed as
https://crrev.com/908a130993076bf98bb5db216bdec2a1919da88b
Cr-Commit-Position: refs/heads/master@{#345863}