Change uses of base::JoinString to pass StringPieces where possible.

components/nacl/renderer/platform_info.cc

 // Copyright 2014 The Chromium 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 "base/cpu.h"
 #include "base/logging.h"
+#include "base/strings/string_piece.h"
 #include "base/strings/string_util.h"
 #include "build/build_config.h"
 #if defined(OS_WIN)
 #include "base/win/windows_version.h"
 #endif
 
 namespace nacl {
 
 const char* GetSandboxArch() {
 #if defined(ARCH_CPU_ARM_FAMILY)
@@ skipping 35 matching lines @@
   // TODO(jfb) Some features are missing, either because the NaCl
   //           sandbox doesn't support them, because base::CPU doesn't
   //           detect them, or because they don't help vector shuffles
   //           (and we omit them because it simplifies testing). Add the
   //           other features.
   //
   // TODO(jfb) The following is x86-specific. The base::CPU class
   //           doesn't handle other architectures very well, and we
   //           should at least detect the presence of ARM's integer
   //           divide.
-  std::vector<std::string> features;
+  std::vector<base::StringPiece> features;
   base::CPU cpu;
 
   // On x86, SSE features are ordered: the most recent one implies the
   // others. Care is taken here to only specify the latest SSE version,
   // whereas non-SSE features don't follow this model: POPCNT is
   // effectively always implied by SSE4.2 but has to be specified
   // separately.
   //
   // TODO: AVX2, AVX, SSE 4.2.
   if (cpu.has_sse41()) features.push_back("+sse4.1");
   // TODO: SSE 4A, SSE 4.
   else if (cpu.has_ssse3()) features.push_back("+ssse3");
   // TODO: SSE 3
   else if (cpu.has_sse2()) features.push_back("+sse2");
 
   if (cpu.has_popcnt()) features.push_back("+popcnt");
 
   // TODO: AES, LZCNT, ...
   return base::JoinString(features, ",");
 }
 
 }  // namespace nacl