Add addCharCode to StringBuffer interface. Already implemented by all implementations.

corelib/src/string_buffer.dart

Index: corelib/src/string_buffer.dart
diff --git a/corelib/src/string_buffer.dart b/corelib/src/string_buffer.dart
index 5d2864107174ebbb6d6d0436e858cbcd4ff0456d..c510ec755f74c739eef363b76544d5b4e027e36e 100644
--- a/corelib/src/string_buffer.dart
+++ b/corelib/src/string_buffer.dart
@@ -24,11 +24,17 @@ interface StringBuffer default StringBufferImpl {
   bool isEmpty();
 
   /**
-   * Adds [obj] to the buffer. Returns [:this:].
+   * Converts [obj] to a string and adds it to the buffer. Returns [:this:].
    */
   StringBuffer add(Object obj);
 
   /**
+   * Adds the string representation of [charCode] to the buffer.
+   * Returns [this].
+   */
+  StringBuffer addCharCode(int charCode);
+
+  /**
    * Adds all items in [objects] to the buffer. Returns [:this:].
    */
   StringBuffer addAll(Collection<Object> objects);