[interpreter] Fix memory leak in Bytecodes::Decode().

src/interpreter/bytecodes.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/bytecodes.h"
 
 #include "src/frames.h"
 #include "src/interpreter/bytecode-traits.h"
 
 namespace v8 {
@@ skipping 466 matching lines @@
       return ReadUnalignedUInt32(operand_start);
     case OperandSize::kNone:
       UNREACHABLE();
   }
   return 0;
 }
 
 // static
 std::ostream& Bytecodes::Decode(std::ostream& os, const uint8_t* bytecode_start,
                                 int parameter_count) {
-  Vector<char> buf = Vector<char>::New(50);
+  ScopedVector<char> buf(50);
 
   Bytecode bytecode = Bytecodes::FromByte(bytecode_start[0]);
   int prefix_offset = 0;
   OperandScale operand_scale = OperandScale::kSingle;
   if (IsPrefixScalingBytecode(bytecode)) {
     prefix_offset = 1;
     operand_scale = Bytecodes::PrefixBytecodeToOperandScale(bytecode);
     bytecode = Bytecodes::FromByte(bytecode_start[1]);
   }
   int bytecode_size = Bytecodes::Size(bytecode, operand_scale);
   for (int i = 0; i < prefix_offset + bytecode_size; i++) {
     SNPrintF(buf, "%02x ", bytecode_start[i]);

[rmcilroy, 2016/03/24 08:51:26]

Could we just use something like:
os << std::width(2) << std::hex() << bytecode_start[i];

Then we could get rid of buf entirely?

     os << buf.start();
   }
   const int kBytecodeColumnSize = 6;
   for (int i = prefix_offset + bytecode_size; i < kBytecodeColumnSize; i++) {
     os << "   ";
   }
 
   os << Bytecodes::ToString(bytecode, operand_scale) << " ";
 
   // Operands for the debug break are from the original instruction.
@@ skipping 167 matching lines @@
   } else {
     std::ostringstream s;
     s << "r" << index();
     return s.str();
   }
 }
 
 }  // namespace interpreter
 }  // namespace internal
 }  // namespace v8