Print more diagnosis info on to-space invariant violation.

Pass the method/field (in GcRootSource) to the read barrier to print
more info when a to-space invariant violation is detected on a
method/field GC root access.

Refactor ConcurrentCopying::AssertToSpaceInvariant().

Bug: 12687968
Bug: 21564728

Change-Id: I3a5fde1f41969349b0fee6cd9217b948d5241a7c
9 files changed