stagefright: update & pass graphic buffer properly to OMX

Update graphic buffer must update the handle in the proper buffer.
E.g. if using emptyBuffer later, it must update the backup buffer
and use the backup buffer's metadata mode which may differ from the
codec buffer's mode.  Also use proper size for filled graphicbuffer.

Bug: 22775369
Change-Id: I9ec7032ed5db4c0636e2e2a4bad32022d251d66b