[debugger] make step positions for for-of compatible with interpreter.

src/interpreter/bytecode-generator.cc

Index: src/interpreter/bytecode-generator.cc
diff --git a/src/interpreter/bytecode-generator.cc b/src/interpreter/bytecode-generator.cc
index ac6873af182ab10d97324fea74cd060f653de510..a81e1726179a27c1ccd10b70fdee885961cb2c21 100644
--- a/src/interpreter/bytecode-generator.cc
+++ b/src/interpreter/bytecode-generator.cc
@@ -1188,6 +1188,7 @@ void BytecodeGenerator::VisitForOfStatement(ForOfStatement* stmt) {
   LoopBuilder loop_builder(builder());
   ControlScopeForIteration control_scope(this, stmt, &loop_builder);
 
+  builder()->SetExpressionAsStatementPosition(stmt->assign_iterator());
   VisitForEffect(stmt->assign_iterator());
 
   loop_builder.LoopHeader();