[interpreter] Implement static loop depth tracking.

src/interpreter/bytecode-generator.h

Index: src/interpreter/bytecode-generator.h
diff --git a/src/interpreter/bytecode-generator.h b/src/interpreter/bytecode-generator.h
index 2def89346746169b38e8dc5308f2f33227e90497..5f6aac5178e02dc38cdbaba86235cdee14d5b57e 100644
--- a/src/interpreter/bytecode-generator.h
+++ b/src/interpreter/bytecode-generator.h
@@ -214,6 +214,7 @@ class BytecodeGenerator final : public AstVisitor<BytecodeGenerator> {
   RegisterAllocationScope* register_allocator_;
   ZoneVector<BytecodeLabel> generator_resume_points_;
   Register generator_state_;
+  int loop_depth_;
 };
 
 }  // namespace interpreter