Fix libcxx build.

ipc/ipc_message_utils.cc

 // Copyright (c) 2012 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 "ipc/ipc_message_utils.h"
 
 #include "base/files/file_path.h"
 #include "base/json/json_writer.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/nullable_string16.h"
@@ skipping 386 matching lines @@
   return true;
 }
 
 void ParamTraits<std::vector<unsigned char> >::Log(const param_type& p,
                                                    std::string* l) {
   LogBytes(p, l);
 }
 
 void ParamTraits<std::vector<bool> >::Write(Message* m, const param_type& p) {
   WriteParam(m, static_cast<int>(p.size()));
+  // Cast to bool below is required because libc++'s
+  // vector<bool>::const_reference is different from bool, and we want to avoid
+  // writing an extra specialization of ParamTraits for it.
   for (size_t i = 0; i < p.size(); i++)
-    WriteParam(m, p[i]);
+    WriteParam(m, static_cast<bool>(p[i]));
 }
 
 bool ParamTraits<std::vector<bool> >::Read(const Message* m,
                                            PickleIterator* iter,
                                            param_type* r) {
   int size;
   // ReadLength() checks for < 0 itself.
   if (!m->ReadLength(iter, &size))
     return false;
   r->resize(size);
   for (int i = 0; i < size; i++) {
     bool value;
     if (!ReadParam(m, iter, &value))
       return false;
     (*r)[i] = value;
   }
   return true;
 }
 
 void ParamTraits<std::vector<bool> >::Log(const param_type& p, std::string* l) {
   for (size_t i = 0; i < p.size(); ++i) {
     if (i != 0)
       l->push_back(' ');
-    LogParam((p[i]), l);
+    LogParam(static_cast<bool>(p[i]), l);
   }
 }
 
 void ParamTraits<DictionaryValue>::Write(Message* m, const param_type& p) {
   WriteValue(m, &p, 0);
 }
 
 bool ParamTraits<DictionaryValue>::Read(
     const Message* m, PickleIterator* iter, param_type* r) {
   int type;
@@ skipping 372 matching lines @@
   return result;
 }
 
 void ParamTraits<MSG>::Log(const param_type& p, std::string* l) {
   l->append("<MSG>");
 }
 
 #endif  // OS_WIN
 
 }  // namespace IPC