Bucket unknown symbols by PC and demangle native symbols

runtime/vm/native_symbol_macos.cc

Index: runtime/vm/native_symbol_macos.cc
diff --git a/runtime/vm/native_symbol_macos.cc b/runtime/vm/native_symbol_macos.cc
index 3b240bdacc5042d3cad7dbb6e7f36f5b44fa1091..4de33cef80b62eb1b3c5cfa9f91a6ee4990fadcc 100644
--- a/runtime/vm/native_symbol_macos.cc
+++ b/runtime/vm/native_symbol_macos.cc
@@ -8,6 +8,7 @@
 #include "vm/native_symbol.h"
 #include "vm/thread.h"
 
+#include <cxxabi.h>  // NOLINT
 #include <dlfcn.h>  // NOLINT
 
 namespace dart {
@@ -29,6 +30,11 @@ char* NativeSymbolResolver::LookupSymbolName(uintptr_t pc) {
   if (info.dli_sname == NULL) {
     return NULL;
   }
+  int status;
+  char* demangled = abi::__cxa_demangle(info.dli_sname, NULL, NULL, &status);
+  if (status == 0) {
+    return demangled;
+  }
   return strdup(info.dli_sname);
 }