Remove String.slice. Too much overlap with String.substring.

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);
   }
 }
 
@@ skipping 139 matching lines @@
     }
     if ((endIndex < 0) || (endIndex > this.length)) {
       throw new RangeError.value(endIndex);
     }
     if (startIndex > endIndex) {
       throw new RangeError.value(startIndex);
     }
     return _substringUnchecked(startIndex, endIndex);
   }
 
-  String slice([int startIndex, int endIndex]) {
-    int start, end;
-    if (startIndex == null) {
-      start = 0;
-    } else if (startIndex is! int) {
-      throw new ArgumentError("startIndex is not int");
-    } else if (startIndex >= 0) {
-      start = startIndex;
-    } else {
-      start = this.length + startIndex;
-    }
-    if (start < 0 || start > this.length) {
-      throw new RangeError(
-          "startIndex out of range: $startIndex (length: $length)");
-    }
-    if (endIndex == null) {
-      end = this.length;
-    } else if (endIndex is! int) {
-      throw new ArgumentError("endIndex is not int");
-    } else if (endIndex >= 0) {
-      end = endIndex;
-    } else {
-      end = this.length + endIndex;
-    }
-    if (end < 0 || end > this.length) {
-      throw new RangeError(
-          "endIndex out of range: $endIndex (length: $length)");
-    }
-    if (end < start) {
-      throw new ArgumentError(
-          "End before start: $endIndex < $startIndex (length: $length)");
-    }
-    return _substringUnchecked(start, end);
-  }
-
   String _substringUnchecked(int startIndex, int endIndex) {
     assert(endIndex != null);
     assert((startIndex >= 0) && (startIndex <= this.length));
     assert((endIndex >= 0) && (endIndex <= this.length));
     assert(startIndex <= endIndex);
 
     if (startIndex == endIndex) {
       return "";
     }
     if ((startIndex + 1) == endIndex) {
@@ skipping 415 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);
 }