Track usage of "this" and "arguments" in Scope

src/ast-value-factory.h

Index: src/ast-value-factory.h
diff --git a/src/ast-value-factory.h b/src/ast-value-factory.h
index 82e6e6bb6a17a2eb3a0ccb9b1bf99132f4ffcf48..09702eb710da199afcf0cefe624c5b720729e29b 100644
--- a/src/ast-value-factory.h
+++ b/src/ast-value-factory.h
@@ -88,6 +88,8 @@ class AstRawString : public AstString {
     return *c;
   }
 
+  V8_INLINE bool IsArguments(AstValueFactory* ast_value_factory) const;
+
   // For storing AstRawStrings in a hash map.
   uint32_t hash() const {
     return hash_;
@@ -340,6 +342,10 @@ class AstValueFactory {
 #undef F
 };
 
+
+bool AstRawString::IsArguments(AstValueFactory* ast_value_factory) const {
+  return ast_value_factory->arguments_string() == this;
+}
 } }  // namespace v8::internal
 
 #undef STRING_CONSTANTS