Avoid using RegExps in path to work around issue 19090.

pkg/path/lib/src/parsed_path.dart

 // Copyright (c) 2013, 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.
 
 library path.parsed_path;
 
 import 'internal_style.dart';
 import 'style.dart';
 
 class ParsedPath {
@@ skipping 34 matching lines @@
 
     // Remove the root prefix, if any.
     var root = style.getRoot(path);
     var isRootRelative = style.getRelativeRoot(path) != null;
     if (root != null) path = path.substring(root.length);
 
     // Split the parts on path separators.
     var parts = [];
     var separators = [];
 
-    var firstSeparator = style.separatorPattern.matchAsPrefix(path);
-    if (firstSeparator != null) {
-      separators.add(firstSeparator[0]);
-      path = path.substring(firstSeparator[0].length);
+    var start = 0;
+
+    if (path.isNotEmpty && style.isSeparator(path.codeUnitAt(0))) {
+      separators.add(path[0]);
+      start = 1;
     } else {
       separators.add('');
     }
 
-    var start = 0;
-    for (var match in style.separatorPattern.allMatches(path)) {
-      parts.add(path.substring(start, match.start));
-      separators.add(match[0]);
-      start = match.end;
+    for (var i = start; i < path.length; i++) {
+      if (style.isSeparator(path.codeUnitAt(i))) {
+        parts.add(path.substring(start, i));
+        separators.add(path[i]);
+        start = i + 1;
+      }
     }
 
     // Add the final part, if any.
     if (start < path.length) {
       parts.add(path.substring(start));
       separators.add('');
     }
 
     return new ParsedPath._(style, root, isRootRelative, parts, separators);
   }
@@ skipping 48 matching lines @@
 
     // If we collapsed down to nothing, do ".".
     if (newParts.length == 0 && !isAbsolute) {
       newParts.add('.');
     }
 
     // Canonicalize separators.
     var newSeparators = new List.generate(
         newParts.length, (_) => style.separator, growable: true);
     newSeparators.insert(0,
-        isAbsolute && newParts.length > 0 &&
-                root.contains(style.needsSeparatorPattern) ?
+        isAbsolute && newParts.length > 0 && style.needsSeparator(root) ?
             style.separator : '');
 
     parts = newParts;
     separators = newSeparators;
 
     // Normalize the Windows root if needed.
     if (root != null && style == Style.windows) {
       root = root.replaceAll('/', '\\');
     }
     removeTrailingSeparators();
@@ skipping 29 matching lines @@
     if (lastDot <= 0) return [file, ''];
 
     return [file.substring(0, lastDot), file.substring(lastDot)];
   }
 
   ParsedPath clone() => new ParsedPath._(
       style, root, isRootRelative,
       new List.from(parts), new List.from(separators));
 }