Give the layout test harness better information to determine when to finish.

Give the layout test harness better information to determine when to finish.

Currently, blink's FrameLoader.cpp contains a complex, hacky function to
determine when to inform the rest of chromium that loading is complete. This
complexity is only necessary to support layout tests. This puts the requisite
logic in the layout test harness. This logic is behind a temporary flag, in
order to permit both blink and chromium to flip to the new definition of load
completion simultaneously.

BUG=

Committed: https://crrev.com/46789a8b27fffe9c4d55b57fd21c3aef1dca1b69
Cr-Commit-Position: refs/heads/master@{#294085}

[Nate Chapin, 2014-09-08 19:58:33]

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

[abarth-chromium, 2014-09-09 23:29:58]

lgtm

[Nate Chapin, 2014-09-09 23:31:58]

The CQ bit was checked by japhet@chromium.org

[commit-bot: I haz the power, 2014-09-09 23:52:05]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/japhet@chromium.org/550343002/20001

[commit-bot: I haz the power, 2014-09-10 03:07:37]

Committed patchset #2 (id:20001) as a0363afe0b812b9e16f83a73da92bbf1d845228c

[commit-bot: I haz the power, 2014-09-10 03:58:36]

Patchset 2 (id:??) landed as
https://crrev.com/46789a8b27fffe9c4d55b57fd21c3aef1dca1b69
Cr-Commit-Position: refs/heads/master@{#294085}