[Interpreter] Implement ForInStep directly.

src/compiler/code-stub-assembler.cc

Index: src/compiler/code-stub-assembler.cc
diff --git a/src/compiler/code-stub-assembler.cc b/src/compiler/code-stub-assembler.cc
index 45f47d3310933dc50a8b8feb7ec5c12149c5a844..52d506679c9c6895b3b290538f6b81aa67794b69 100644
--- a/src/compiler/code-stub-assembler.cc
+++ b/src/compiler/code-stub-assembler.cc
@@ -72,6 +72,9 @@ Node* CodeStubAssembler::NumberConstant(double value) {
   return raw_assembler_->NumberConstant(value);
 }
 
+Node* CodeStubAssembler::SmiConstant(Smi* value) {
+  return IntPtrConstant(bit_cast<intptr_t>(value));
+}
 
 Node* CodeStubAssembler::HeapConstant(Handle<HeapObject> object) {
   return raw_assembler_->HeapConstant(object);
@@ -125,6 +128,8 @@ Node* CodeStubAssembler::SmiUntag(Node* value) {
   return raw_assembler_->WordSar(value, SmiShiftBitsConstant());
 }
 
+Node* CodeStubAssembler::SmiAdd(Node* a, Node* b) { return IntPtrAdd(a, b); }
+
 #define DEFINE_CODE_STUB_ASSEMBER_BINARY_OP(name)   \
   Node* CodeStubAssembler::name(Node* a, Node* b) { \
     return raw_assembler_->name(a, b);              \