[interpreter] Fix debug stepping for generators.

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 231a9a25af01946fce1a4374bf3b96b467c67e9c..5bb0986b39ead35c7a6b30718aaab5847babe30e 100644
--- a/src/interpreter/bytecode-array-builder.cc
+++ b/src/interpreter/bytecode-array-builder.cc
@@ -536,6 +536,7 @@ BytecodeArrayBuilder& BytecodeArrayBuilder::ReThrow() {
 }
 
 BytecodeArrayBuilder& BytecodeArrayBuilder::Return() {
+  SetReturnPosition();
   Output(Bytecode::kReturn);
   return_seen_in_block_ = true;
   return *this;
@@ -630,7 +631,6 @@ BytecodeArrayBuilder& BytecodeArrayBuilder::MarkTryEnd(int handler_id) {
 void BytecodeArrayBuilder::EnsureReturn() {
   if (!return_seen_in_block_) {
     LoadUndefined();
-    SetReturnPosition();
     Return();
   }
   DCHECK(return_seen_in_block_);