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 4beff01fcdecfa0046fc915828726ff8a9cc151d..58082b0dc53eb56c694b0653489f7e48abbdd3f6 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_;
@@ -337,6 +339,11 @@ 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