Reduce the number of Uris parsed in builtin.

runtime/bin/dartutils.cc

Index: runtime/bin/dartutils.cc
diff --git a/runtime/bin/dartutils.cc b/runtime/bin/dartutils.cc
index 25aa2f2f8eb8e155e0b6cb672f2b7c31ae03b723..1a963d132765fd21c030c713d8572fbf7922226a 100644
--- a/runtime/bin/dartutils.cc
+++ b/runtime/bin/dartutils.cc
@@ -380,10 +380,6 @@ Dart_Handle DartUtils::LibraryTagHandler(Dart_LibraryTag tag,
     // Resolve the url within the context of the library's URL.
     Dart_Handle builtin_lib =
         Builtin::LoadAndCheckLibrary(Builtin::kBuiltinLibrary);
-    Dart_Handle library_url = Dart_LibraryUrl(library);
-    if (Dart_IsError(library_url)) {
-      return library_url;
-    }
     return ResolveUri(library_url, url, builtin_lib);
   }