Canonicalize uris in C++ instead of Dart for the standalone embedder.

runtime/vm/uri.h

+// 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.
+
+#ifndef VM_URI_H_
+#define VM_URI_H_
+
+#include "platform/utils.h"
+#include "vm/globals.h"
+
+namespace dart {
+
+struct ParsedUri {
+  const char* scheme;
+  const char* userinfo;
+  const char* host;
+  const char* port;
+  const char* path;
+  const char* query;
+  const char* fragment;
+};
+
+// Parses a uri into its parts.  Returns false if the parse fails.
+bool ParseUri(const char* uri, ParsedUri* parsed_uri);
+
+// Resolves some reference uri with respect to a base uri.
+bool ResolveUri(const char* ref_uri,
+                const char* base_uri,
+                const char** target_uri);
+
+}  // namespace dart
+
+#endif  // VM_URI_H_