[Interpreter] Add support for for..in.

src/interpreter/control-flow-builders.cc

Index: src/interpreter/control-flow-builders.cc
diff --git a/src/interpreter/control-flow-builders.cc b/src/interpreter/control-flow-builders.cc
index 6c634bbe841d277566cf29884f35c7ab078d878d..4dc00fe981377ee4ab4ba0fd5423fe2f1b47d097 100644
--- a/src/interpreter/control-flow-builders.cc
+++ b/src/interpreter/control-flow-builders.cc
@@ -31,6 +31,12 @@ void LoopBuilder::EmitJump(ZoneVector<BytecodeLabel>* sites) {
 }
 
 
+void LoopBuilder::EmitJumpIfTrue(ZoneVector<BytecodeLabel>* sites) {
+  sites->push_back(BytecodeLabel());
+  builder()->JumpIfTrue(&sites->back());
+}
+
+
 void LoopBuilder::BindLabels(const BytecodeLabel& target,
                              ZoneVector<BytecodeLabel>* sites) {
   for (size_t i = 0; i < sites->size(); i++) {