null value can be the receiver of methods on Object (e.g. hashCode).

runtime/vm/il_printer.cc

Index: runtime/vm/il_printer.cc
diff --git a/runtime/vm/il_printer.cc b/runtime/vm/il_printer.cc
index c4d74e5411b508758475efb1fb95cdd4ffa49ff2..d938145143ecc1d6ba87c6e85252de074894a778 100644
--- a/runtime/vm/il_printer.cc
+++ b/runtime/vm/il_printer.cc
@@ -32,6 +32,14 @@ void BufferFormatter::VPrint(const char* format, va_list args) {
 }
 
 
+void FlowGraphPrinter::PrintGraph(const char* phase, FlowGraph* flow_graph) {
+  OS::Print("*** BEGIN CFG\n%s\n", phase);
+  FlowGraphPrinter printer(*flow_graph);
+  printer.PrintBlocks();
+  OS::Print("*** END CFG\n");
+}
+
+
 void FlowGraphPrinter::PrintBlocks() {
   if (!function_.IsNull()) {
     OS::Print("==== %s\n", function_.ToFullyQualifiedCString());