servo: Merge #19569 - Add a topLevelDomComplete metric (from asajeffrey:script-perf-measure-topLevelDomComplete); r=jdm

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

Measure DOM completion without iframes. This is in support of measuring when the main document is loaded, ignoring secondary content, e.g. ads.

---
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- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes fix #19561
- [X] There are tests for these changes

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Source-Repo: https://github.com/servo/servo
Source-Revision: d832e1b8f843612b4cb124d8c4eb9dce94e92d50

--HG--
extra : subtree_source : https%3A//hg.mozilla.org/projects/converted-servo-linear
extra : subtree_revision : 377138e2fc2d7d65866ba238978ba0e30ae910b0

servo/components/script/document_loader.rs

@@ -141,6 +141,13 @@ impl DocumentLoader {
         !self.blocking_loads.is_empty()
     }
 
+    pub fn is_only_blocked_by_iframes(&self) -> bool {
+        self.blocking_loads.iter().all(|load| match *load {
+            LoadType::Subframe(_) => true,
+            _ => false
+        })
+    }
+
     pub fn inhibit_events(&mut self) {
         self.events_inhibited = true;
     }

servo/components/script/dom/document.rs

@@ -322,6 +322,7 @@ pub struct Document {
     dom_content_loaded_event_start: Cell<u64>,
     dom_content_loaded_event_end: Cell<u64>,
     dom_complete: Cell<u64>,
+    top_level_dom_complete: Cell<u64>,
     load_event_start: Cell<u64>,
     load_event_end: Cell<u64>,
     /// <https://html.spec.whatwg.org/multipage/#concept-document-https-state>
@@ -1627,6 +1628,12 @@ impl Document {
         // asap_in_order_script_loaded.
 
         let loader = self.loader.borrow();
+
+        // Servo measures when the top-level content (not iframes) is loaded.
+        if (self.top_level_dom_complete.get() == 0) && loader.is_only_blocked_by_iframes() {
+            update_with_current_time_ms(&self.top_level_dom_complete);
+        }
+
         if loader.is_blocked() || loader.events_inhibited() {
             // Step 6.
             return;
@@ -1951,6 +1958,10 @@ impl Document {
         self.dom_complete.get()
     }
 
+    pub fn get_top_level_dom_complete(&self) -> u64 {
+        self.top_level_dom_complete.get()
+    }
+
     pub fn get_load_event_start(&self) -> u64 {
         self.load_event_start.get()
     }
@@ -2265,6 +2276,7 @@ impl Document {
             dom_content_loaded_event_start: Cell::new(Default::default()),
             dom_content_loaded_event_end: Cell::new(Default::default()),
             dom_complete: Cell::new(Default::default()),
+            top_level_dom_complete: Cell::new(Default::default()),
             load_event_start: Cell::new(Default::default()),
             load_event_end: Cell::new(Default::default()),
             https_state: Cell::new(HttpsState::None),

servo/components/script/dom/performancetiming.rs

@@ -86,6 +86,12 @@ impl PerformanceTimingMethods for PerformanceTiming {
     fn LoadEventEnd(&self) -> u64 {
         self.document.get_load_event_end()
     }
+
+    // check-tidy: no specs after this line
+    // Servo-only timing for when top-level content (not iframes) is complete
+    fn TopLevelDomComplete(&self) -> u64 {
+        self.document.get_top_level_dom_complete()
+    }
 }
 
 

servo/components/script/dom/webidls/PerformanceTiming.webidl

@@ -29,4 +29,7 @@ interface PerformanceTiming {
   readonly attribute unsigned long long domComplete;
   readonly attribute unsigned long long loadEventStart;
   readonly attribute unsigned long long loadEventEnd;
+  /* Servo-onnly attribute for measuring when the top-level document (not iframes) is complete. */
+  [Pref="dom.testperf.enabled"]
+  readonly attribute unsigned long long topLevelDomComplete;
 };