Work around http://bugs.java.com/bugdatabase/view_bug.do?bug_id=5041014 :
URLClassLoader, on Windows, locks the .jar file forever.
As of Java 7, there's a workaround: you can call close() when you're "done"
with the file. We'll do that here. However, the whole point of the
JarFileIssueRegistry is that when lint is run over and over again
as the user is editing in the IDE and we're background checking the code, we
don't to keep loading the custom view classes over and over again: we want to
cache them. Therefore, just closing the URLClassLoader right away isn't great
either. However, it turns out it's safe to close the URLClassLoader once you've
loaded the classes you need, since the URLClassLoader will continue to serve
those classes even after its close() methods has been called.
Therefore, if we can call close() on this URLClassLoader, we'll proactively load
all class files we find in the .jar file, then close it.