[Interpreter] Add support for for..in.

src/interpreter/bytecode-array-builder.h

Index: src/interpreter/bytecode-array-builder.h
diff --git a/src/interpreter/bytecode-array-builder.h b/src/interpreter/bytecode-array-builder.h
index 15ff07e93d056db3ce4624854a95045b75128c4e..83fd4ebd5c30d90b7bbff6ce998c828a9f2b6d7b 100644
--- a/src/interpreter/bytecode-array-builder.h
+++ b/src/interpreter/bytecode-array-builder.h
@@ -185,6 +185,11 @@ class BytecodeArrayBuilder {
   BytecodeArrayBuilder& Throw();
   BytecodeArrayBuilder& Return();
 
+  // Complex flow control.
+  BytecodeArrayBuilder& ForInPrepare();
+  BytecodeArrayBuilder& ForInNext(Register for_in_state);
+  BytecodeArrayBuilder& ForInDone(Register for_in_state);
+
   BytecodeArrayBuilder& EnterBlock();
   BytecodeArrayBuilder& LeaveBlock();
 
@@ -282,7 +287,7 @@ class BytecodeLabel final {
     bound_ = true;
   }
   INLINE(void set_referrer(size_t offset)) {
-    DCHECK(!bound_ && offset != kInvalidOffset);
+    DCHECK(!bound_ && offset != kInvalidOffset && offset_ == kInvalidOffset);
     offset_ = offset;
   }
   INLINE(size_t offset() const) { return offset_; }