In Tiger, we moved a lot of the GC validation code for the X11 pipeline up to the
Java level for improved performance (see 4900269). Unfortunately, those changes
only affected X11Renderer (due to time constraints), so other methods that require GC
validation were left unchanged, such as X11PMBlitLoops and X11TextRenderer. This
meant that we ended up with two mostly redundant code paths, one for Java-level
validation, and one at the native level. We should refactor the code added in
4900269 so that is useful outside of X11Renderer and so we can eliminate the
redundant code path.

Also, we are proposing to update the existing AWT lock to use ReentrantLock for
improved performance (see 6317330). The changes proposed here will ensure that we
get better performance from that change by locking at the Java level rather than
using the native AWT_LOCK() macros.