[Interpreter] Add support for for count operations.

src/interpreter/interpreter.h

Index: src/interpreter/interpreter.h
diff --git a/src/interpreter/interpreter.h b/src/interpreter/interpreter.h
index cb68bf671bf0216c1f1306ca8a526cf5ba6d486a..6bd15078bef92e090630ff84396dfb656b9f8259 100644
--- a/src/interpreter/interpreter.h
+++ b/src/interpreter/interpreter.h
@@ -54,6 +54,10 @@ class Interpreter {
   void DoBinaryOp(Runtime::FunctionId function_id,
                   compiler::InterpreterAssembler* assembler);
 
+  // Generates code to perform the count operations via |function_id|.
+  void DoCountOp(Runtime::FunctionId function_id,
+                 compiler::InterpreterAssembler* assembler);
+
   // Generates code to perform the comparison operation associated with
   // |compare_op|.
   void DoCompareOp(Token::Value compare_op,