Fix a FORWARD_NULL defect in ExtractModuleName reported by Coverity....

Fix a FORWARD_NULL defect in ExtractModuleName reported by Coverity.
If 'sep' is still NULL after the for loop, ix must be -1, so
ix == 0 cannot be true.

Update the comment for ExtractModuleName in the header to match
the implementation.  I don't see any code that checks whether the
path is a full path.

R=rvargas
BUG=http://crbug.com/17101
TEST=none

Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=21404

[wtc, 2009-07-23 01:51:02]

If ExtractModuleName should check whether the path is a
full path, I will undo my change to the comment in the
header file and add a TODO comment to the .cc file instead.

[rvargas (doing something else), 2009-07-23 02:54:13]

LGTM.

The current behavior is the desired one, thanks.