Move map data into backtrace data proper.

The backtrace structure used to include a pointer to a backtrace_map_t
that represented the map data for a particular pc. This introduced a
race condition where the pointer could be discarded, but the backtrace
structure still contained a pointer to garbage memory. Now all of the map
information is right in the structure.

Bug: 19028453
Change-Id: If7088a73f3c6bf1f3bc8cdd2bb4b62e7cab831c0
diff --git a/libbacktrace/UnwindMap.h b/libbacktrace/UnwindMap.h
index 2fdb29f..be8855e 100644
--- a/libbacktrace/UnwindMap.h
+++ b/libbacktrace/UnwindMap.h
@@ -45,7 +45,7 @@
 
   virtual bool Build();
 
-  virtual const backtrace_map_t* Find(uintptr_t addr);
+  virtual void FillIn(uintptr_t addr, backtrace_map_t* map);
 
 protected:
   virtual bool GenerateMap();