NBLog: add buffer hex dump

Bug: 36724290
Test: create and print entries, check dump matches expected content
Change-Id: I71c4df287535b460838afc2d3ce651744850bf49
diff --git a/media/libnbaio/include/NBLog.h b/media/libnbaio/include/NBLog.h
index d116ec6..f2fdf12 100644
--- a/media/libnbaio/include/NBLog.h
+++ b/media/libnbaio/include/NBLog.h
@@ -261,7 +261,8 @@
     static void    appendPID(String8 *body, const void *data, size_t length);
     static void    appendTimestamp(String8 *body, const void *data);
     static size_t  fmtEntryLength(const uint8_t *data);
-
+    static String8 bufferHexDump(const uint8_t *buffer, size_t size);
+    static String8 bufferHexDump(const EntryIterator &it);
 public:
 
 // Located in shared memory, must be POD.