Auto merge of #12552 - ConnorGBrewster:history_interface, r=asajeffrey

History interface Go, Back, and Forward

<!-- Please describe your changes on the following line: -->
r? @asajeffrey

---
<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `__` with appropriate data: -->
- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes fix #5670 (github issue number if applicable).

<!-- Either: -->
- [X] There are tests for these changes OR
- [ ] These changes do not require tests because _____

<!-- Pull requests that do not address these steps are welcome, but they will require additional verification as part of the review process. -->

implement go, forward, back

<!-- 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/12552)
<!-- Reviewable:end -->

1 files changed, 8 insertions, 0 deletions

diff --git a/components/script/dom/window.rs b/components/script/dom/window.rs
index b4984bb2a4a..2237514bd3d 100644
--- a/components/script/dom/window.rs
+++ b/components/script/dom/window.rs
@@ -30,6 +30,7 @@ use dom::document::Document;
 use dom::element::Element;
 use dom::event::Event;
 use dom::eventtarget::EventTarget;
+use dom::history::History;
 use dom::htmliframeelement::build_mozbrowser_custom_event;
 use dom::location::Location;
 use dom::navigator::Navigator;
@@ -158,6 +159,7 @@ pub struct Window {
     #[ignore_heap_size_of = "channels are hard"]
     image_cache_chan: ImageCacheChan,
     browsing_context: MutNullableHeap<JS<BrowsingContext>>,
+    history: MutNullableHeap<JS<History>>,
     performance: MutNullableHeap<JS<Performance>>,
     navigation_start: u64,
     navigation_start_precise: f64,
@@ -475,6 +477,11 @@ impl WindowMethods for Window {
         self.browsing_context().active_document()
     }
 
+    // https://html.spec.whatwg.org/multipage/#dom-history
+    fn History(&self) -> Root<History> {
+        self.history.or_init(|| History::new(self))
+    }
+
     // https://html.spec.whatwg.org/multipage/#dom-location
     fn Location(&self) -> Root<Location> {
         self.Document().GetLocation().unwrap()
@@ -1648,6 +1655,7 @@ impl Window {
             mem_profiler_chan: mem_profiler_chan,
             time_profiler_chan: time_profiler_chan,
             devtools_chan: devtools_chan,
+            history: Default::default(),
             browsing_context: Default::default(),
             performance: Default::default(),
             navigation_start: (current_time.sec * 1000 + current_time.nsec as i64 / 1000000) as u64,