Fix the weird names that can occur in exceptions and logs when there is no

Fix the weird names that can occur in exceptions and logs when there is no
mock qualifier and due to the method names getting wrapped in quotes.

To help this work properly, we now assert that a Mock has a name if it is 
passed in a LogEntryList, as opposed to allocating its own. We already said
in the comments that this was a requirement but it wasn't enforced. 
Committed: https://code.google.com/p/dart/source/detail?r=9613

[Siggi Cherem (dart-lang), 2012-07-12 20:56:06]

lgtm