Store library paths relative to a given application root folder.

pkg/kernel/lib/application_root.dart

Index: pkg/kernel/lib/application_root.dart
diff --git a/pkg/kernel/lib/application_root.dart b/pkg/kernel/lib/application_root.dart
new file mode 100644
index 0000000000000000000000000000000000000000..a65d8dd0bf12c4ce1c58daa5f6242877be678f75
--- /dev/null
+++ b/pkg/kernel/lib/application_root.dart
@@ -0,0 +1,45 @@
+// Copyright (c) 2016, 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 kernel.application_root;
+
+import 'package:path/path.dart' as pathlib;
+
+/// Resolves URIs with the `app` scheme.
+///
+/// These are used internally in kernel to represent file paths relative to
+/// some application root. This is done to avoid storing irrelevant paths, such
+/// as the path to the home directory of the user who compiled a given file.
+class ApplicationRoot {
+  static const String scheme = 'app';
+
+  final String path;
+
+  ApplicationRoot(this.path) {
+    assert(path == null || pathlib.isAbsolute(path));
+  }
+
+  ApplicationRoot.none() : path = null;
+
+  /// Converts `app` URIs to absolute `file` URIs.
+  Uri absoluteUri(Uri uri) {
+    if (path == null) return uri;
+    if (uri.scheme == ApplicationRoot.scheme) {
+      return new Uri(scheme: 'file', path: pathlib.join(this.path, uri.path));
+    } else {
+      return uri;
+    }
+  }
+
+  /// Converts `file` URIs to `app` URIs.
+  Uri relativeUri(Uri uri) {
+    if (path == null) return uri;
+    if (uri.scheme == 'file' && pathlib.isWithin(this.path, uri.path)) {
+      return new Uri(
+          scheme: ApplicationRoot.scheme,
+          path: pathlib.relative(uri.path, from: this.path));
+    } else {
+      return uri;
+    }
+  }
+}