Auto merge of #22714 - aditj:patch-3, r=jdm

Added fetch_start functionality

<!-- Please describe your changes on the following line: -->
Added the fetch_start functionality in http_loader.rs (http_fetch function)

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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 #21258 (GitHub issue number if applicable)

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

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components/script/dom/performanceresourcetiming.rs

@@ -78,7 +78,7 @@ impl PerformanceResourceTiming {
             entry: PerformanceEntry::new_inherited(
                 DOMString::from(url.into_string()),
                 DOMString::from("resource"),
-                fetch_start,
+                0.,
                 0.,
             ),
             initiator_type: initiator_type,
@@ -118,7 +118,7 @@ impl PerformanceResourceTiming {
             worker_start: 0.,
             redirect_start: 0.,
             redirect_end: 0.,
-            fetch_start: 0.,
+            fetch_start: resource_timing.fetch_start as f64,
             domain_lookup_start: 0.,
             domain_lookup_end: 0.,
             connect_start: 0.,
@@ -184,4 +184,9 @@ impl PerformanceResourceTimingMethods for PerformanceResourceTiming {
         // TODO
         Finite::wrap(self.response_start)
     }
+
+    // https://w3c.github.io/resource-timing/#dom-performanceresourcetiming-fetchstart
+    fn FetchStart(&self) -> DOMHighResTimeStamp {
+        Finite::wrap(self.fetch_start)
+    }
 }

components/script/dom/webidls/PerformanceResourceTiming.webidl

@@ -6,6 +6,7 @@
  * https://w3c.github.io/resource-timing/
  */
 
+// https://w3c.github.io/resource-timing/#sec-performanceresourcetiming
 [Exposed=(Window,Worker)]
 interface PerformanceResourceTiming : PerformanceEntry {
     readonly attribute DOMString           initiatorType;
@@ -13,7 +14,7 @@ interface PerformanceResourceTiming : PerformanceEntry {
     // readonly attribute DOMHighResTimeStamp workerStart;
     // readonly attribute DOMHighResTimeStamp redirectStart;
     // readonly attribute DOMHighResTimeStamp redirectEnd;
-    // readonly attribute DOMHighResTimeStamp fetchStart;
+    readonly attribute DOMHighResTimeStamp fetchStart;
     // readonly attribute DOMHighResTimeStamp domainLookupStart;
     // readonly attribute DOMHighResTimeStamp domainLookupEnd;
     // readonly attribute DOMHighResTimeStamp connectStart;
@@ -27,9 +28,3 @@ interface PerformanceResourceTiming : PerformanceEntry {
     /// readonly attribute unsigned long long  decodedBodySize;
     // [Default] object toJSON();
 };
-
-// partial interface Performance {
-//  void clearResourceTimings();
-//  void setResourceTimingBufferSize(unsigned long maxSize);
-//              attribute EventHandler onresourcetimingbufferfull;
-// };