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

mojo/public/cpp/bindings/lib/map_internal.h

Index: mojo/public/cpp/bindings/lib/map_internal.h
diff --git a/mojo/public/cpp/bindings/lib/map_internal.h b/mojo/public/cpp/bindings/lib/map_internal.h
index aa0fe7ee4218fe71c459ebd23a4cebac18c62650..f006cd011ae86033a2c5c56e9864eb70b55da23b 100644
--- a/mojo/public/cpp/bindings/lib/map_internal.h
+++ b/mojo/public/cpp/bindings/lib/map_internal.h
@@ -57,7 +57,7 @@ struct MapTraits<Key, Value, false> {
   static inline ValueRefType at(std::map<KeyStorageType, ValueStorageType>* m,
                                 KeyForwardType key) {
     // We don't have C++11 library support yet, so we have to emulate the crash
-    // on a non-existant key.
+    // on a non-existent key.
     auto it = m->find(key);
     MOJO_CHECK(it != m->end());
     return it->second;
@@ -66,11 +66,17 @@ struct MapTraits<Key, Value, false> {
       const std::map<KeyStorageType, ValueStorageType>* m,
       KeyForwardType key) {
     // We don't have C++11 library support yet, so we have to emulate the crash
-    // on a non-existant key.
+    // on a non-existent key.
     auto it = m->find(key);
     MOJO_CHECK(it != m->end());
     return it->second;
   }
+  static inline ValueRefType GetOrInsert(
+      std::map<KeyStorageType, ValueStorageType>* m,
+      KeyForwardType key) {
+    // This is the backing for the index operator (operator[]).
+    return (*m)[key];
+  }
   static inline void Insert(std::map<KeyStorageType, ValueStorageType>* m,
                             KeyForwardType key,
                             ValueForwardType value) {
@@ -146,7 +152,7 @@ struct MapTraits<Key, Value, true> {
   static inline ValueRefType at(std::map<KeyStorageType, ValueStorageType>* m,
                                 KeyForwardType key) {
     // We don't have C++11 library support yet, so we have to emulate the crash
-    // on a non-existant key.
+    // on a non-existent key.
     auto it = m->find(key);
     MOJO_CHECK(it != m->end());
     return GetValue(it);
@@ -155,11 +161,23 @@ struct MapTraits<Key, Value, true> {
       const std::map<KeyStorageType, ValueStorageType>* m,
       KeyForwardType key) {
     // We don't have C++11 library support yet, so we have to emulate the crash
-    // on a non-existant key.
+    // on a non-existent key.
     auto it = m->find(key);
     MOJO_CHECK(it != m->end());
     return GetValue(it);
   }
+  static inline ValueRefType GetOrInsert(
+      std::map<KeyStorageType, ValueStorageType>* m,
+      KeyForwardType key) {
+    // This is the backing for the index operator (operator[]).
+    auto it = m->find(key);
+    if (it == m->end()) {
+      it = m->insert(std::make_pair(key, ValueStorageType())).first;
+      new (it->second.buf) Value();
+    }
+
+    return GetValue(it);
+  }
   static inline void Insert(std::map<KeyStorageType, ValueStorageType>* m,
                             KeyForwardType key,
                             ValueRefType value) {