Fix background compilation: allocate stubs at safepoint

runtime/vm/compiler.cc

Index: runtime/vm/compiler.cc
diff --git a/runtime/vm/compiler.cc b/runtime/vm/compiler.cc
index 4d88bae6e9dee1d12b6b29cba97285bdc2bf6c4c..103792a44df86dc6a3c4d750a61f933f00561e66 100644
--- a/runtime/vm/compiler.cc
+++ b/runtime/vm/compiler.cc
@@ -1153,9 +1153,10 @@ static RawError* CompileFunctionHelper(CompilationPipeline* pipeline,
     if (trace_compiler) {
       const intptr_t token_size = function.end_token_pos().Pos() -
                                   function.token_pos().Pos();
-      THR_Print("Compiling %s%sfunction: '%s' @ token %s, size %" Pd "\n",
+      THR_Print("Compiling %s%sfunction %s: '%s' @ token %s, size %" Pd "\n",
                 (osr_id == Compiler::kNoOSRDeoptId ? "" : "osr "),
                 (optimized ? "optimized " : ""),
+                (Compiler::IsBackgroundCompilation() ? "(background)" : ""),
                 function.ToFullyQualifiedCString(),
                 function.token_pos().ToCString(),
                 token_size);