Auto merge of #11698 - aneeshusa:remove-subpage-id, r=notriddle

Excise SubpageId and use only PipelineIds

<!-- Please describe your changes on the following line: -->

SubpageId was originally introduced in 2013 to help iframes keep track of
their associated (children) pipelines. However, since each pipeline
already has a PipelineId, and those are unique, those are sufficient
to keep track of children.

---
<!-- 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 #11694  (github issue number if applicable).

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- [ ] There are tests for these changes OR
- [X] These changes do not require tests because refactoring

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1 files changed, 9 insertions, 23 deletions

diff --git a/components/script/dom/window.rs b/components/script/dom/window.rs
index e8006123360..f4efcd8dd76 100644
--- a/components/script/dom/window.rs
+++ b/components/script/dom/window.rs
@@ -51,7 +51,7 @@ use js::jsval::UndefinedValue;
 use js::rust::CompileOptionsWrapper;
 use js::rust::Runtime;
 use libc;
-use msg::constellation_msg::{FrameType, LoadData, PipelineId, SubpageId, WindowSizeType};
+use msg::constellation_msg::{FrameType, LoadData, PipelineId, WindowSizeType};
 use net_traits::ResourceThreads;
 use net_traits::bluetooth_thread::BluetoothMethodMsg;
 use net_traits::image_cache_thread::{ImageCacheChan, ImageCacheThread};
@@ -200,16 +200,14 @@ pub struct Window {
     /// page changes.
     devtools_wants_updates: Cell<bool>,
 
-    next_subpage_id: Cell<SubpageId>,
-
     /// Pending resize event, if any.
     resize_event: Cell<Option<(WindowSizeData, WindowSizeType)>>,
 
     /// Pipeline id associated with this page.
     id: PipelineId,
 
-    /// Subpage id associated with this page, if any.
-    parent_info: Option<(PipelineId, SubpageId, FrameType)>,
+    /// Parent id associated with this page, if any.
+    parent_info: Option<(PipelineId, FrameType)>,
 
     /// Global static data related to the DOM.
     dom_static: GlobalStaticData,
@@ -331,15 +329,11 @@ impl Window {
         worker_id
     }
 
-    pub fn pipeline(&self) -> PipelineId {
+    pub fn pipeline_id(&self) -> PipelineId {
         self.id
     }
 
-    pub fn subpage(&self) -> Option<SubpageId> {
-        self.parent_info.map(|p| p.1)
-    }
-
-    pub fn parent_info(&self) -> Option<(PipelineId, SubpageId, FrameType)> {
+    pub fn parent_info(&self) -> Option<(PipelineId, FrameType)> {
         self.parent_info
     }
 
@@ -472,7 +466,7 @@ impl WindowMethods for Window {
         }
 
         let (sender, receiver) = ipc::channel().unwrap();
-        self.constellation_chan().send(ConstellationMsg::Alert(self.pipeline(), s.to_string(), sender)).unwrap();
+        self.constellation_chan().send(ConstellationMsg::Alert(self.pipeline_id(), s.to_string(), sender)).unwrap();
 
         let should_display_alert_dialog = receiver.recv().unwrap();
         if should_display_alert_dialog {
@@ -1058,7 +1052,7 @@ impl Window {
         // TODO (farodin91): Raise an event to stop the current_viewport
         self.update_viewport_for_scroll(x, y);
 
-        let message = ConstellationMsg::ScrollFragmentPoint(self.pipeline(), layer_id, point, smooth);
+        let message = ConstellationMsg::ScrollFragmentPoint(self.pipeline_id(), layer_id, point, smooth);
         self.constellation_chan.send(message).unwrap();
     }
 
@@ -1492,13 +1486,6 @@ impl Window {
         WindowProxyHandler(self.dom_static.windowproxy_handler.0)
     }
 
-    pub fn get_next_subpage_id(&self) -> SubpageId {
-        let subpage_id = self.next_subpage_id.get();
-        let SubpageId(id_num) = subpage_id;
-        self.next_subpage_id.set(SubpageId(id_num + 1));
-        subpage_id
-    }
-
     pub fn get_pending_reflow_count(&self) -> u32 {
         self.pending_reflow_count.get()
     }
@@ -1612,7 +1599,7 @@ impl Window {
     // https://html.spec.whatwg.org/multipage/#top-level-browsing-context
     pub fn is_top_level(&self) -> bool {
         match self.parent_info {
-            Some((_, _, FrameType::IFrame)) => false,
+            Some((_, FrameType::IFrame)) => false,
             _ => true,
         }
     }
@@ -1676,7 +1663,7 @@ impl Window {
                timer_event_chan: IpcSender<TimerEvent>,
                layout_chan: Sender<Msg>,
                id: PipelineId,
-               parent_info: Option<(PipelineId, SubpageId, FrameType)>,
+               parent_info: Option<(PipelineId, FrameType)>,
                window_size: Option<WindowSizeData>)
                -> Root<Window> {
         let layout_rpc: Box<LayoutRPC> = {
@@ -1726,7 +1713,6 @@ impl Window {
             page_clip_rect: Cell::new(max_rect()),
             fragment_name: DOMRefCell::new(None),
             resize_event: Cell::new(None),
-            next_subpage_id: Cell::new(SubpageId(0)),
             layout_chan: layout_chan,
             layout_rpc: layout_rpc,
             window_size: Cell::new(window_size),