Temporary fix for CWS client redirect issue to undo a regression.

Temporary fix for CWS client redirect issue to undo a regression.

This re-introduces a smaller bug fixed by r231370 until the underlying
problem in WebDataSource::replacesCurrentHistoryItem is resolved.

BUG=313572, 311271
TEST=Try to add an app in CWS when not signed in.  Go back from signin page.
R=nasko@chromium.org

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=233454

[Charlie Reis, 2013-11-06 23:01:42]

Nasko, can you review?

I hate to put the bug back in, but I think this might be the quickest fix until
Nate untangles replacesCurrentHistoryItem.  Reasons to proceed with it:
1) I don't know of any concrete cases my original fix affected, so undoing it
isn't so bad.
2) There's a very real case with the CWS that's broken at the moment.
3) While the same bug is theoretically possible on non-WebUI pages even after
this CL, I can't find any repro steps for that at the moment.

Ultimately, this can go away once we fix replacesCurrentHistoryItem.

[nasko, 2013-11-06 23:06:56]

Urgh, ugly, but oh well. LGTM

[Charlie Reis, 2013-11-07 01:03:58]

Committed patchset #1 manually as r233454 (presubmit successful).