Clean up the TestRunner methods exposed for Web Notifications.

Clean up the TestRunner methods exposed for Web Notifications.

Rename simulateLegacyWebNotificationClick to simulateWebNotificationClick
since it is not specific to legacy notifications. Also remove the
cancelAllActiveNotifications method, since it's not currently used
and resetting notifications will be done automatically between tests.

BUG=349015
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=256638

[Peter Beverloo, 2014-03-04 16:58:51]

These should be the last TestRunner-side changes, as I think I can write most
other tests I've got planned with the code as it is.

These changes will be reflected by "notification-click.html" in:
  https://codereview.chromium.org/186713002/

[Andrew T Wilson (Slow), 2014-03-04 21:46:57]

lgtm

[pfeldman, 2014-03-05 15:15:50]

rslgtm

[Peter Beverloo, 2014-03-12 17:31:38]

The CQ bit was checked by peter@chromium.org

[commit-bot: I haz the power, 2014-03-12 17:32:28]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/peter@chromium.org/184313005/60001

[commit-bot: I haz the power, 2014-03-12 19:25:58]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/peter@chromium.org/184313005/60001

[commit-bot: I haz the power, 2014-03-12 20:53:57]

Change committed as 256638