Auto merge of #16804 - hiikezoe:allow-unitless-length-for-smil, r=birtles

Allow unitless length for smil

This is a PR for https://bugzilla.mozilla.org/show_bug.cgi?id=1363574

- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes do not require tests because it's for stylo

<!-- Reviewable:start -->
---
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/16804)
<!-- Reviewable:end -->

components/style/gecko/generated/bindings.rs

@@ -4,7 +4,6 @@ pub use nsstring::{nsACString, nsAString, nsString};
 type nsACString_internal = nsACString;
 type nsAString_internal = nsAString;
 use gecko_bindings::structs::mozilla::css::GridTemplateAreasValue;
-#[allow(unused_imports)]
 use gecko_bindings::structs::mozilla::css::ImageValue;
 use gecko_bindings::structs::mozilla::css::URLValue;
 use gecko_bindings::structs::mozilla::Side;
@@ -1815,7 +1814,8 @@ extern "C" {
 extern "C" {
     pub fn Servo_ParseProperty(property: nsCSSPropertyID,
                                value: *const nsACString,
-                               data: *mut RawGeckoURLExtraData)
+                               data: *mut RawGeckoURLExtraData,
+                               length_parsing_mode: LengthParsingMode)
      -> RawServoDeclarationBlockStrong;
 }
 extern "C" {