Add operator<< for mojo::String for logging use

mojo/public/cpp/bindings/string.h

 // 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.
 
 #ifndef MOJO_PUBLIC_CPP_BINDINGS_STRING_H_
 #define MOJO_PUBLIC_CPP_BINDINGS_STRING_H_
 
 #include <string>
 
 #include "mojo/public/cpp/bindings/lib/array_internal.h"
@@ skipping 88 matching lines @@
 inline bool operator==(const char* a, const String& b) {
   return !b.is_null() && a == b.get();
 }
 inline bool operator==(const String& a, const char* b) {
   return !a.is_null() && a.get() == b;
 }
 inline bool operator!=(const String& a, const String& b) { return !(a == b); }
 inline bool operator!=(const char* a, const String& b) { return !(a == b); }
 inline bool operator!=(const String& a, const char* b) { return !(a == b); }
 
+inline std::ostream& operator<<(std::ostream& out, const String& s) {
+  return out << s.get();
+}
+
 // TODO(darin): Add similar variants of operator<,<=,>,>=
 
 template <>
 class TypeConverter<String, std::string> {
  public:
   static String ConvertFrom(const std::string& input) {
     return String(input);
   }
   static std::string ConvertTo(const String& input) {
     return input;
@@ skipping 24 matching lines @@
  public:
   // |input| may be null, in which case a null String will be returned.
   static String ConvertFrom(const char* input) {
     return String(input);
   }
 };
 
 }  // namespace mojo
 
 #endif  // MOJO_PUBLIC_CPP_BINDINGS_STRING_H_