Improve java.nio.Buffer.toString.

Bug: https://code.google.com/p/android/issues/detail?id=53637
Change-Id: I823662b39cb48b5f4456f4c58269324dfcdc2fd1
Remove dead NioUtils.getDirectBufferAddress.

Change-Id: I764d86db1d74c5daf54cc925a9fc76db15a1107a