iExploder stops periodically, failing to redirect to the next test. A case that I reduced was a test having an IFRAME with "about:plugins" SRC.
Created attachment 9288 [details] Test case
The about:plugins part should be fixable by amending a hack in Frame::loadSubframe(), which knows about:blank, but not other about: URLs. The other case (unknown scheme, such as foo:bar) looks more complex - a policy delegate inside Safari tells WebKit to ignore the load, and so it does.
Also filed as <rdar://problem/4622333>.
The attached test case seems to work now. See Bug 14716 Comment #7.
Looks like we don't need two bugs for this, and the other one has better test cases. *** This bug has been marked as a duplicate of 14716 ***