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

src/interpreter/bytecode-array-builder.h

 // 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.
 
 #ifndef V8_INTERPRETER_BYTECODE_ARRAY_BUILDER_H_
 #define V8_INTERPRETER_BYTECODE_ARRAY_BUILDER_H_
 
 #include "src/ast/ast.h"
 #include "src/interpreter/bytecode-array-writer.h"
 #include "src/interpreter/bytecode-register-allocator.h"
@@ skipping 294 matching lines @@
       // latest value.
       latest_source_info_.MakeExpressionPosition(expr->position());
     }
   }
 
   void SetExpressionAsStatementPosition(Expression* expr) {
     if (expr->position() == kNoSourcePosition) return;
     latest_source_info_.MakeStatementPosition(expr->position());
   }
 
-  void EnsureReturn();
+  bool RequiresImplicitReturn() const { return !return_seen_in_block_; }
 
   // Accessors
   BytecodeRegisterAllocator* register_allocator() {
     return &register_allocator_;
   }
   const BytecodeRegisterAllocator* register_allocator() const {
     return &register_allocator_;
   }
   Zone* zone() const { return zone_; }
 
@@ skipping 79 matching lines @@
   static int const kNoFeedbackSlot = 0;
 
   DISALLOW_COPY_AND_ASSIGN(BytecodeArrayBuilder);
 };
 
 }  // namespace interpreter
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_INTERPRETER_BYTECODE_ARRAY_BUILDER_H_