Optimize OneByteString’s contains function for one character patterns (similar to indexOf).

runtime/lib/string_patch.dart

 // Copyright (c) 2012, 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.
 
 patch class String {
   /* patch */ factory String.fromCharCodes(Iterable<int> charCodes) {
     return _StringBase.createFromCharCodes(charCodes);
   }
 
   /* patch */ const factory String.fromEnvironment(String name,
@@ skipping 584 matching lines @@
           if (this.codeUnitAt(i) == patternCu0) {
             return i;
           }
         }
         return -1;
       }
     }
     return super.indexOf(pattern, start);
   }
 
+  bool contains(Pattern pattern, [int start = 0]) {
+    final pCid = pattern._cid;
+    if ((pCid == _OneByteString._classId) ||
+        (pCid == _TwoByteString._classId) ||
+        (pCid == _ExternalOneByteString._classId)) {
+      final len = this.length;
+      if ((pattern.length == 1) && (start >= 0) && (start < len)) {
+        final patternCu0 = pattern.codeUnitAt(0);
+        if (patternCu0 > 0xFF) {
+          return false;
+        }
+        for (int i = start; i < len; i++) {
+          if (this.codeUnitAt(i) == patternCu0) {
+            return true;
+          }
+        }
+        return false;
+      }
+    }
+    return super.contains(pattern, start);
+  }
+
   // Allocates a string of given length, expecting its content to be
   // set using _setAt.
   static _OneByteString _allocate(int length) native "OneByteString_allocate";
 
   // This is internal helper method. Code point value must be a valid
   // Latin1 value (0..0xFF), index must be valid.
   void _setAt(int index, int codePoint) native "OneByteString_setAt";
 }
 
 
@@ skipping 86 matching lines @@
 class _CodeUnits extends Object with ListMixin<int>,
                                      UnmodifiableListMixin<int> {
   /** The string that this is the code units of. */
   String _string;
 
   _CodeUnits(this._string);
 
   int get length => _string.length;
   int operator[](int i) => _string.codeUnitAt(i);
 }