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

runtime/bin/builtin.dart

Index: runtime/bin/builtin.dart
diff --git a/runtime/bin/builtin.dart b/runtime/bin/builtin.dart
index 6b16d994551827de5ae466d623cc1eaafb690ffd..112fa45fe89af41b3b602cf1411876798fbd2b21 100644
--- a/runtime/bin/builtin.dart
+++ b/runtime/bin/builtin.dart
@@ -691,25 +691,6 @@ _loadDataAsync(int tag, String uri, String libraryUri) {
 }
 
 
-// Embedder Entrypoint:
-// Function called by standalone embedder to resolve uris when the VM requests
-// Dart_kCanonicalizeUrl from the tag handler.
-String _resolveUri(String base, String userString) {
-  if (!_setupCompleted) {
-    _setupHooks();
-  }
-  if (_traceLoading) {
-    _log('Resolving: $userString from $base');
-  }
-  var baseUri = Uri.parse(base);
-  var result = baseUri.resolve(userString).toString();
-  if (_traceLoading) {
-    _log('Resolved $userString in $base to $result');
-  }
-  return result;
-}
-
-
 // Handling of access to the package root or package map from user code.
 _triggerPackageResolution(action) {
   if (_packagesReady) {