Modify the logic to launch external browser (only for target=_content
and target=_blank links). Also add something to DocShellLoadInfo
so that a user of nsDocShell::LoadURI can specify the target desired.
this is needed to implement things like open attachment so we can make the doc shell
think a user click happened when it talks to the uriloader.
I removed two boolean fields which were representing two load types. Simplified the api by allowing you
to pass in any of our load types.
r=valeski