[Interpreter] Ensure that implicit return undefined is generated.

src/interpreter/bytecode-array-builder.cc

Index: src/interpreter/bytecode-array-builder.cc
diff --git a/src/interpreter/bytecode-array-builder.cc b/src/interpreter/bytecode-array-builder.cc
index dba816d61810d63259412f946f219494c2e134ef..5f97bce75b2f34184e3cd99753aebe084317169a 100644
--- a/src/interpreter/bytecode-array-builder.cc
+++ b/src/interpreter/bytecode-array-builder.cc
@@ -37,6 +37,12 @@ void BytecodeArrayBuilder::set_parameter_count(int number_of_parameters) {
 int BytecodeArrayBuilder::parameter_count() const { return parameter_count_; }
 
 
+bool BytecodeArrayBuilder::HasExplicitReturn() {
+  return !bytecodes_.empty() &&
+         bytecodes_.back() == Bytecodes::ToByte(Bytecode::kReturn);
+}
+
+
 Register BytecodeArrayBuilder::Parameter(int parameter_index) {
   DCHECK_GE(parameter_index, 0);
   DCHECK_LT(parameter_index, parameter_count_);