[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 fa57c16c7cca85c9faa418815cddf63dd0620b3e..bdb9caea2a88360bd337831f2f7220bc6a76a3a1 100644
--- a/src/interpreter/bytecode-array-builder.cc
+++ b/src/interpreter/bytecode-array-builder.cc
@@ -517,6 +517,7 @@ BytecodeArrayBuilder& BytecodeArrayBuilder::ReThrow() {
 }
 
 BytecodeArrayBuilder& BytecodeArrayBuilder::Return() {
+  SetReturnPosition();
   Output(Bytecode::kReturn);
   return_seen_in_block_ = true;
   return *this;
@@ -611,7 +612,6 @@ BytecodeArrayBuilder& BytecodeArrayBuilder::MarkTryEnd(int handler_id) {
 void BytecodeArrayBuilder::EnsureReturn() {
   if (!return_seen_in_block_) {
     LoadUndefined();
-    SetReturnPosition();
     Return();
   }
   DCHECK(return_seen_in_block_);