[interpreter] Implement static loop depth tracking.

src/interpreter/bytecode-generator.h

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_INTERPRETER_BYTECODE_GENERATOR_H_
 #define V8_INTERPRETER_BYTECODE_GENERATOR_H_
 
 #include "src/ast/ast.h"
 #include "src/interpreter/bytecode-array-builder.h"
 #include "src/interpreter/bytecode-label.h"
@@ skipping 194 matching lines @@
   BytecodeArrayBuilder* builder_;
   CompilationInfo* info_;
   Scope* scope_;
   ZoneVector<Handle<Object>> globals_;
   ControlScope* execution_control_;
   ContextScope* execution_context_;
   ExpressionResultScope* execution_result_;
   RegisterAllocationScope* register_allocator_;
   ZoneVector<BytecodeLabel> generator_resume_points_;
   Register generator_state_;
+  int loop_depth_;
 };
 
 }  // namespace interpreter
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_INTERPRETER_BYTECODE_GENERATOR_H_