Setup R10/EDX to be valid Oops before stub calls

runtime/vm/intermediate_language_arm64.cc

Index: runtime/vm/intermediate_language_arm64.cc
diff --git a/runtime/vm/intermediate_language_arm64.cc b/runtime/vm/intermediate_language_arm64.cc
index 9f4cc1300d67f2f463b1e6132ef823e82e46b2ac..71f4cac54b010529459bb4f680c959169417abb6 100644
--- a/runtime/vm/intermediate_language_arm64.cc
+++ b/runtime/vm/intermediate_language_arm64.cc
@@ -5332,6 +5332,19 @@ void AllocateObjectInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
   __ Drop(ArgumentCount());  // Discard arguments.
 }
 
+
+void DebugStepCheckInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
+  ASSERT(!compiler->is_optimizing());
+  const ExternalLabel label(StubCode::DebugStepCheckEntryPoint());
+  __ LoadImmediate(R4, 0, kNoPP);
+  __ LoadImmediate(R5, 0, kNoPP);
+  compiler->GenerateCall(token_pos(), &label, stub_kind_, locs());
+#if defined(DEBUG)
+  __ LoadImmediate(R4, 1, kNoPP);  // Garbage that looks like an object.
+  __ LoadImmediate(R5, 1, kNoPP);
+#endif
+}
+
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_ARM64