mojo: Switch the clipboard interface over to using map<>.

mojo/public/cpp/bindings/map.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_MAP_H_
 #define MOJO_PUBLIC_CPP_BINDINGS_MAP_H_
 
 #include <map>
 
 #include "mojo/public/cpp/bindings/lib/map_internal.h"
@@ skipping 70 matching lines @@
   void insert(KeyForwardType key, ValueForwardType value) {
     is_null_ = false;
     Traits::Insert(&map_, key, value);
   }
 
   ValueRefType at(KeyForwardType key) { return Traits::at(&map_, key); }
   ValueConstRefType at(KeyForwardType key) const {
     return Traits::at(&map_, key);
   }
 
+  ValueRefType operator[](KeyForwardType key) {
+    is_null_ = false;
+    return Traits::GetOrInsert(&map_, key);
+  }
+
   void Swap(Map<Key, Value>* other) {
     std::swap(is_null_, other->is_null_);
     map_.swap(other->map_);
   }
   void Swap(std::map<Key, Value>* other) {
     is_null_ = false;
     map_.swap(*other);
   }
 
   // This moves all values in the map to a set of parallel arrays. This action
@@ skipping 115 matching lines @@
             TypeConverter<STLValue, MojoValue>::Convert(it.GetValue())));
       }
     }
     return result;
   }
 };
 
 }  // namespace mojo
 
 #endif  // MOJO_PUBLIC_CPP_BINDINGS_MAP_H_