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

sdk/lib/_internal/compiler/implementation/lib/js_string.dart

Index: sdk/lib/_internal/compiler/implementation/lib/js_string.dart
diff --git a/sdk/lib/_internal/compiler/implementation/lib/js_string.dart b/sdk/lib/_internal/compiler/implementation/lib/js_string.dart
index e6184c0d893fc9fe19a4db0f3bc1b97c00464754..56a494daee63d7b666ce7fea20fa0e0b46946e91 100644
--- a/sdk/lib/_internal/compiler/implementation/lib/js_string.dart
+++ b/sdk/lib/_internal/compiler/implementation/lib/js_string.dart
@@ -89,42 +89,6 @@ class JSString extends Interceptor implements String, JSIndexable {
     return JS('String', r'#.substring(#, #)', this, 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 JS('String', '#.substring(#, #)', this, start, end);
-  }
-
-
   String toLowerCase() {
     return JS('String', r'#.toLowerCase()', this);
   }