Setup R10/EDX to be valid Oops before stub calls

runtime/vm/intermediate_language_ia32.cc

Index: runtime/vm/intermediate_language_ia32.cc
diff --git a/runtime/vm/intermediate_language_ia32.cc b/runtime/vm/intermediate_language_ia32.cc
index 71b9fb665f98a229b4cc38cd3a64392dd9f88459..78f616d63f9c6cf84369968bd085fbf70c823870 100644
--- a/runtime/vm/intermediate_language_ia32.cc
+++ b/runtime/vm/intermediate_language_ia32.cc
@@ -6296,6 +6296,19 @@ void AllocateObjectInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
   __ Drop(ArgumentCount());  // Discard arguments.
 }
 
+
+void DebugStepCheckInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
+  ASSERT(!compiler->is_optimizing());
+  const ExternalLabel label(StubCode::DebugStepCheckEntryPoint());
+  __ movl(EDX, Immediate(0));
+  __ movl(ECX, Immediate(0));
+  compiler->GenerateCall(token_pos(), &label, stub_kind_, locs());
+#if defined(DEBUG)
+  __ movl(EDX, Immediate(1));  // Garbage that looks like an object.
+  __ movl(EDX, Immediate(1));
+#endif
+}
+
 }  // namespace dart
 
 #undef __