Correct a misnomer regarding supplementary code points.

runtime/vm/unicode.h

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef VM_UNICODE_H_
 #define VM_UNICODE_H_
 
 #include "vm/allocation.h"
 #include "vm/globals.h"
 
 namespace dart {
 
 class String;
 
 class Utf8 : AllStatic {
  public:
   enum Type {
-    kLatin1 = 0,  // Latin-1 character set.
-    kBMP,  // Basic Multilingual Plane.
-    kSMP,  // Supplementary Multilingual Plane.
+    kLatin1 = 0,  // Latin-1 code point [U+0000, U+00FF].
+    kBMP,  // Basic Multilingual Plane code point [U+0000, U+FFFF].
+    kSupplementary,  // Supplementary code point [U+010000, U+10FFFF].
   };
 
   static const intptr_t kMaxOneByteChar   = 0x7F;
   static const intptr_t kMaxTwoByteChar   = 0x7FF;
   static const intptr_t kMaxThreeByteChar = 0xFFFF;
   static const intptr_t kMaxFourByteChar  = 0x10FFFF;
 
   static intptr_t CodePointCount(const uint8_t* utf8_array,
                                  intptr_t array_len,
                                  Type* type);
@@ skipping 131 matching lines @@
   // Data for small code points with one mapping
   static const int16_t stage2_[];
 
   // Data for large code points or code points with both mappings.
   static const int32_t stage2_exception_[][2];
 };
 
 }  // namespace dart
 
 #endif  // VM_UNICODE_H_