[interpreter] Implement support for the --trace flag.

src/interpreter/bytecode-array-builder.h

Index: src/interpreter/bytecode-array-builder.h
diff --git a/src/interpreter/bytecode-array-builder.h b/src/interpreter/bytecode-array-builder.h
index efee1f4e1ba07e85d340c8e9aaf32efa689575c3..ab817b637a7120d0bb6186b5d0622b9c358dc5bf 100644
--- a/src/interpreter/bytecode-array-builder.h
+++ b/src/interpreter/bytecode-array-builder.h
@@ -312,7 +312,7 @@ class BytecodeArrayBuilder final : public ZoneObject {
     latest_source_info_.MakeStatementPosition(expr->position());
   }
 
-  void EnsureReturn();
+  bool RequiresImplicitReturn() const { return !return_seen_in_block_; }
 
   // Accessors
   BytecodeRegisterAllocator* register_allocator() {