Don't throw when there is an "onError" for int.parse.

runtime/lib/integers_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.
 // Dart core library.
 
 // VM implementation of int.
 
 patch class int {
 
   static bool _isWhitespace(int codePoint) {
@@ skipping 56 matching lines @@
 
   static int _native_parse(String str) native "Integer_parse";
 
   static int _throwFormatException(String source) {
     throw new FormatException(source);
   }
 
   /* patch */ static int parse(String source,
                                { int radix,
                                  int onError(String str) }) {
-    if ((radix == null) && (onError == null)) return _parse(source);
+    if (radix == null) {
+      int result = _parse(source);
+      if (result == null) {
+        if (onError == null) {
+          throw new FormatException(source);
+        }
+        return onError(source);
+      }
+      return result;
+    }
     return _slowParse(source, radix, onError);
   }
 
   static int _slowParse(String source, int radix, int onError(String str)) {
     if (source is! String) throw new ArgumentError(source);
-    if (radix == null) {
-      assert(onError != null);
-      try {
-        return _parse(source);
-      } on FormatException {
-        return onError(source);
-      }
-    }
     if (radix is! int) throw new ArgumentError("Radix is not an integer");
     if (radix < 2 || radix > 36) {
       throw new RangeError("Radix $radix not in range 2..36");
     }
     if (onError == null) {
       onError = _throwFormatException;
     }
     // Remove leading and trailing white space.
     source = source.trim();
     if (source.isEmpty) return onError(source);
@@ skipping 25 matching lines @@
       int digit = digits[code - 0x30];
       if (digit >= radix) return onError(source);
       result = result * radix + digit;
       i++;
       if (i == source.length) break;
       code = source.codeUnitAt(i);
     } while (true);
     return negative ? -result : result;
   }
 }