Fix multi-line hex dumping and add unit test.

Change-Id: I7657018fef5d9c17410a9a634db275555f180014
diff --git a/build/Android.gtest.mk b/build/Android.gtest.mk
index bed48ba..acaa0f8 100644
--- a/build/Android.gtest.mk
+++ b/build/Android.gtest.mk
@@ -30,6 +30,7 @@
 	compiler/utils/x86/managed_register_x86_test.cc \
 	runtime/barrier_test.cc \
 	runtime/base/bit_vector_test.cc \
+	runtime/base/hex_dump_test.cc \
 	runtime/base/histogram_test.cc \
 	runtime/base/mutex_test.cc \
 	runtime/base/timing_logger_test.cc \