[interpreter] Fix debug stepping for generators.

src/interpreter/bytecode-array-builder.cc

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/interpreter/bytecode-array-builder.h"
 
 #include "src/compiler.h"
 #include "src/interpreter/bytecode-array-writer.h"
 #include "src/interpreter/bytecode-label.h"
 #include "src/interpreter/bytecode-peephole-optimizer.h"
@@ skipping 518 matching lines @@
   Output(Bytecode::kThrow);
   return *this;
 }
 
 BytecodeArrayBuilder& BytecodeArrayBuilder::ReThrow() {
   Output(Bytecode::kReThrow);
   return *this;
 }
 
 BytecodeArrayBuilder& BytecodeArrayBuilder::Return() {
+  SetReturnPosition();
   Output(Bytecode::kReturn);
   return_seen_in_block_ = true;
   return *this;
 }
 
 BytecodeArrayBuilder& BytecodeArrayBuilder::Debugger() {
   Output(Bytecode::kDebugger);
   return *this;
 }
 
@@ skipping 74 matching lines @@
 BytecodeArrayBuilder& BytecodeArrayBuilder::MarkTryEnd(int handler_id) {
   BytecodeLabel try_end;
   Bind(&try_end);
   handler_table_builder()->SetTryRegionEnd(handler_id, try_end.offset());
   return *this;
 }
 
 void BytecodeArrayBuilder::EnsureReturn() {
   if (!return_seen_in_block_) {
     LoadUndefined();
-    SetReturnPosition();
     Return();
   }
   DCHECK(return_seen_in_block_);
 }
 
 BytecodeArrayBuilder& BytecodeArrayBuilder::Call(Register callable,
                                                  Register receiver_args,
                                                  size_t receiver_args_count,
                                                  int feedback_slot,
                                                  TailCallMode tail_call_mode) {
@@ skipping 402 matching lines @@
 }
 
 uint32_t BytecodeArrayBuilder::UnsignedOperand(size_t value) {
   DCHECK_LE(value, kMaxUInt32);
   return static_cast<uint32_t>(value);
 }
 
 }  // namespace interpreter
 }  // namespace internal
 }  // namespace v8