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, 6 insertions, 3 deletions

diff --git a/components/script/dom/xmlhttprequest.rs b/components/script/dom/xmlhttprequest.rs
index a97dc7f802b..c23b97b48d7 100644
--- a/components/script/dom/xmlhttprequest.rs
+++ b/components/script/dom/xmlhttprequest.rs
@@ -278,7 +278,7 @@ impl LoadOrigin for XMLHttpRequest {
     }
     fn pipeline_id(&self) -> Option<PipelineId> {
         let global = self.global();
-        Some(global.r().pipeline())
+        Some(global.r().pipeline_id())
     }
 }
 
@@ -1189,7 +1189,7 @@ impl XMLHttpRequest {
         let decoded = charset.decode(&self.response.borrow(), DecoderTrap::Replace).unwrap();
         let document = self.new_doc(IsHTMLDocument::HTMLDocument);
         // TODO: Disable scripting while parsing
-        parse_html(document.r(), DOMString::from(decoded), wr.get_url(), ParseContext::Owner(Some(wr.pipeline())));
+        parse_html(document.r(), DOMString::from(decoded), wr.get_url(), ParseContext::Owner(Some(wr.pipeline_id())));
         document
     }
 
@@ -1200,7 +1200,10 @@ impl XMLHttpRequest {
         let decoded = charset.decode(&self.response.borrow(), DecoderTrap::Replace).unwrap();
         let document = self.new_doc(IsHTMLDocument::NonHTMLDocument);
         // TODO: Disable scripting while parsing
-        parse_xml(document.r(), DOMString::from(decoded), wr.get_url(), xml::ParseContext::Owner(Some(wr.pipeline())));
+        parse_xml(document.r(),
+                  DOMString::from(decoded),
+                  wr.get_url(),
+                  xml::ParseContext::Owner(Some(wr.pipeline_id())));
         document
     }