Add an event time parameter to didStartProvisionalLoad callbacks

Add an event time parameter to didStartProvisionalLoad callbacks

This removes the only caller of WebDataSource::triggeringEventTime(),
which is transient data we probably shouldn't be stashing on a long-lived class anyway.

BUG=

Committed: https://crrev.com/69a06300b7a90448bcd803115955765920c240fc
Cr-Commit-Position: refs/heads/master@{#308145}

[Nate Chapin, 2014-12-11 23:37:43]

japhet@chromium.org changed reviewers:
+ nasko@chromium.org

[Nate Chapin, 2014-12-11 23:37:43]

blink-side: http://src.chromium.org/viewvc/blink?view=revision&revision=186990

This will help enable some cleanup in blink's loader. See
https://codereview.chromium.org/790383002/ for the draft of the followup.

[nasko, 2014-12-11 23:56:03]

LGTM

[Nate Chapin, 2014-12-12 18:25:30]

The CQ bit was checked by japhet@chromium.org

[commit-bot: I haz the power, 2014-12-12 18:26:13]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/799643003/1

[commit-bot: I haz the power, 2014-12-12 19:37:24]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2014-12-12 19:38:08]

Patchset 1 (id:??) landed as
https://crrev.com/69a06300b7a90448bcd803115955765920c240fc
Cr-Commit-Position: refs/heads/master@{#308145}