libbacktrace: export offline unwinding failures.

This is to help debugging different offline unwiding failures.

Bug: http://b/69383534
Test: run backtrace_test.
Change-Id: I5ed4837027a9f17d032925e97e9f5927161444b3
diff --git a/libbacktrace/BacktraceOffline.h b/libbacktrace/BacktraceOffline.h
index 70a9842..fcde379 100644
--- a/libbacktrace/BacktraceOffline.h
+++ b/libbacktrace/BacktraceOffline.h
@@ -32,9 +32,7 @@
   uint64_t end;
   const uint8_t* data;
 
-  Space() {
-    Clear();
-  }
+  Space() { Clear(); }
 
   void Clear();
   size_t Read(uint64_t addr, uint8_t* buffer, size_t size);