Simplify frame loads in OriginReplication and SandboxFlagsReplication tests.

Simplify frame loads in OriginReplication and SandboxFlagsReplication tests.

Recent work on didStopLoading makes it possible for us to use
WaitForLoadStop to wait for all child frames to be loaded when
navigating a subframe.

BUG=

Committed: https://crrev.com/54dee8e8bab33b439b4973cdcfb961e7d0d0b6e4
Cr-Commit-Position: refs/heads/master@{#330155}

[alexmos, 2015-05-15 18:49:53]

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

[alexmos, 2015-05-15 18:49:53]

Hey Nasko, can you please take a look?  This should make these two tests
friendier to your patch.

[nasko, 2015-05-15 18:56:18]

LGTM

[alexmos, 2015-05-15 18:56:34]

The CQ bit was checked by alexmos@chromium.org

[commit-bot: I haz the power, 2015-05-15 18:57:39]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1123233005/1

[commit-bot: I haz the power, 2015-05-15 19:07:11]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-05-15 19:08:04]

Patchset 1 (id:??) landed as
https://crrev.com/54dee8e8bab33b439b4973cdcfb961e7d0d0b6e4
Cr-Commit-Position: refs/heads/master@{#330155}