in java/io/bazel/rules/closure/webfiles/WebfilesValidator.java [212:224]
private static boolean shouldIgnoreUri(String uri) {
return uri.isEmpty()
|| uri.startsWith("#")
|| uri.endsWith("/")
|| uri.contains("//")
|| uri.startsWith("data:")
|| uri.startsWith("javascript:")
|| uri.startsWith("mailto:")
|| uri.equals("about:blank")
// The following are intended to filter out URLs with Polymer variables.
|| (uri.contains("[[") && uri.contains("]]"))
|| (uri.contains("{{") && uri.contains("}}"));
}