Fix multi-line hex dumping and add unit test.

Change-Id: I7657018fef5d9c17410a9a634db275555f180014
diff --git a/runtime/Android.mk b/runtime/Android.mk
index 9e6d5f9..c180b17 100644
--- a/runtime/Android.mk
+++ b/runtime/Android.mk
@@ -23,6 +23,7 @@
 	barrier.cc \
 	base/allocator.cc \
 	base/bit_vector.cc \
+	base/hex_dump.cc \
 	base/logging.cc \
 	base/mutex.cc \
 	base/stringpiece.cc \