Auto merge of #25659 - pshaughn:timingresolution, r=jdm,nox

Expose DOMHighResTimeStamps at lower res

As explained in https://www.w3.org/TR/hr-time-2/#clock-resolution and tested in a few WPT tests, we're not supposed to show Javascript the full resolution of OS timestamps. This fixes that on all the DOMHighResTimeStamp interfaces that weren't already limiting themselves to integer milliseconds.

The specific choice of how to coarsen the resolution is extremely bikesheddable; I commented the reasoning for my arbitrary choice but I admit it's arbitrary.

A couple tests of timing resolution still fail, but because they're seeing undefined and NaN values due to unimplemented attributes (#25658).

---
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- [X] These changes fix #25656 fix #25296 fix #21276

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components/script/dom/event.rs

@@ -10,7 +10,6 @@ use crate::dom::bindings::codegen::Bindings::PerformanceBinding::DOMHighResTimeS
 use crate::dom::bindings::codegen::Bindings::PerformanceBinding::PerformanceBinding::PerformanceMethods;
 use crate::dom::bindings::error::Fallible;
 use crate::dom::bindings::inheritance::Castable;
-use crate::dom::bindings::num::Finite;
 use crate::dom::bindings::refcounted::Trusted;
 use crate::dom::bindings::reflector::{reflect_dom_object, DomObject, Reflector};
 use crate::dom::bindings::root::{DomRoot, DomSlice, MutNullableDom};
@@ -19,6 +18,7 @@ use crate::dom::document::Document;
 use crate::dom::eventtarget::{CompiledEventListener, EventTarget, ListenerPhase};
 use crate::dom::globalscope::GlobalScope;
 use crate::dom::node::Node;
+use crate::dom::performance::reduce_timing_resolution;
 use crate::dom::virtualmethods::vtable_for;
 use crate::dom::window::Window;
 use crate::task::TaskOnce;
@@ -333,7 +333,7 @@ impl EventMethods for Event {
 
     // https://dom.spec.whatwg.org/#dom-event-timestamp
     fn TimeStamp(&self) -> DOMHighResTimeStamp {
-        Finite::wrap(
+        reduce_timing_resolution(
             (self.precise_time_ns - (*self.global().performance().TimeOrigin()).round() as u64)
                 .to_ms(),
         )

components/script/dom/performance.rs

@@ -401,12 +401,12 @@ impl PerformanceMethods for Performance {
 
     // https://dvcs.w3.org/hg/webperf/raw-file/tip/specs/HighResolutionTime/Overview.html#dom-performance-now
     fn Now(&self) -> DOMHighResTimeStamp {
-        Finite::wrap(self.now())
+        reduce_timing_resolution(self.now())
     }
 
     // https://www.w3.org/TR/hr-time-2/#dom-performance-timeorigin
     fn TimeOrigin(&self) -> DOMHighResTimeStamp {
-        Finite::wrap(self.navigation_start_precise as f64)
+        reduce_timing_resolution(self.navigation_start_precise as f64)
     }
 
     // https://www.w3.org/TR/performance-timeline-2/#dom-performance-getentries
@@ -525,3 +525,14 @@ impl PerformanceMethods for Performance {
         SetOnresourcetimingbufferfull
     );
 }
+
+// https://www.w3.org/TR/hr-time-2/#clock-resolution
+pub fn reduce_timing_resolution(exact: f64) -> DOMHighResTimeStamp {
+    // We need a granularity no finer than 5 microseconds.
+    // 5 microseconds isn't an exactly representable f64 so WPT tests
+    // might occasionally corner-case on rounding.
+    // web-platform-tests/wpt#21526 wants us to use an integer number of
+    // microseconds; the next divisor of milliseconds up from 5 microseconds
+    // is 10, which is 1/100th of a millisecond.
+    Finite::wrap((exact * 100.0).floor() / 100.0)
+}

components/script/dom/performanceentry.rs

@@ -2,13 +2,14 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
+use crate::dom::bindings::codegen::Bindings::PerformanceBinding::DOMHighResTimeStamp;
 use crate::dom::bindings::codegen::Bindings::PerformanceEntryBinding;
 use crate::dom::bindings::codegen::Bindings::PerformanceEntryBinding::PerformanceEntryMethods;
-use crate::dom::bindings::num::Finite;
 use crate::dom::bindings::reflector::{reflect_dom_object, Reflector};
 use crate::dom::bindings::root::DomRoot;
 use crate::dom::bindings::str::DOMString;
 use crate::dom::globalscope::GlobalScope;
+use crate::dom::performance::reduce_timing_resolution;
 use dom_struct::dom_struct;
 
 #[dom_struct]
@@ -77,12 +78,12 @@ impl PerformanceEntryMethods for PerformanceEntry {
     }
 
     // https://w3c.github.io/performance-timeline/#dom-performanceentry-starttime
-    fn StartTime(&self) -> Finite<f64> {
-        Finite::wrap(self.start_time)
+    fn StartTime(&self) -> DOMHighResTimeStamp {
+        reduce_timing_resolution(self.start_time)
     }
 
     // https://w3c.github.io/performance-timeline/#dom-performanceentry-duration
-    fn Duration(&self) -> Finite<f64> {
-        Finite::wrap(self.duration)
+    fn Duration(&self) -> DOMHighResTimeStamp {
+        reduce_timing_resolution(self.duration)
     }
 }

components/script/dom/performanceresourcetiming.rs

@@ -6,11 +6,11 @@ use crate::dom::bindings::codegen::Bindings::PerformanceBinding::DOMHighResTimeS
 use crate::dom::bindings::codegen::Bindings::PerformanceResourceTimingBinding::{
     self, PerformanceResourceTimingMethods,
 };
-use crate::dom::bindings::num::Finite;
 use crate::dom::bindings::reflector::reflect_dom_object;
 use crate::dom::bindings::root::DomRoot;
 use crate::dom::bindings::str::DOMString;
 use crate::dom::globalscope::GlobalScope;
+use crate::dom::performance::reduce_timing_resolution;
 use crate::dom::performanceentry::PerformanceEntry;
 use dom_struct::dom_struct;
 use net_traits::ResourceFetchTiming;
@@ -182,17 +182,17 @@ impl PerformanceResourceTimingMethods for PerformanceResourceTiming {
 
     // https://w3c.github.io/resource-timing/#dom-performanceresourcetiming-domainlookupstart
     fn DomainLookupStart(&self) -> DOMHighResTimeStamp {
-        Finite::wrap(self.domain_lookup_start)
+        reduce_timing_resolution(self.domain_lookup_start)
     }
 
     // https://w3c.github.io/resource-timing/#dom-performanceresourcetiming-domainlookupend
     fn DomainLookupEnd(&self) -> DOMHighResTimeStamp {
-        Finite::wrap(self.domain_lookup_end)
+        reduce_timing_resolution(self.domain_lookup_end)
     }
 
     // https://w3c.github.io/resource-timing/#dom-performanceresourcetiming-secureconnectionstart
     fn SecureConnectionStart(&self) -> DOMHighResTimeStamp {
-        Finite::wrap(self.secure_connection_start)
+        reduce_timing_resolution(self.secure_connection_start)
     }
 
     // https://w3c.github.io/resource-timing/#dom-performanceresourcetiming-transfersize
@@ -212,41 +212,41 @@ impl PerformanceResourceTimingMethods for PerformanceResourceTiming {
 
     // https://w3c.github.io/resource-timing/#dom-performanceresourcetiming-requeststart
     fn RequestStart(&self) -> DOMHighResTimeStamp {
-        Finite::wrap(self.request_start)
+        reduce_timing_resolution(self.request_start)
     }
 
     // https://w3c.github.io/resource-timing/#dom-performanceresourcetiming-redirectstart
     fn RedirectStart(&self) -> DOMHighResTimeStamp {
-        Finite::wrap(self.redirect_start)
+        reduce_timing_resolution(self.redirect_start)
     }
 
     // https://w3c.github.io/resource-timing/#dom-performanceresourcetiming-redirectend
     fn RedirectEnd(&self) -> DOMHighResTimeStamp {
-        Finite::wrap(self.redirect_end)
+        reduce_timing_resolution(self.redirect_end)
     }
 
     // https://w3c.github.io/resource-timing/#dom-performanceresourcetiming-responsestart
     fn ResponseStart(&self) -> DOMHighResTimeStamp {
-        Finite::wrap(self.response_start)
+        reduce_timing_resolution(self.response_start)
     }
 
     // https://w3c.github.io/resource-timing/#dom-performanceresourcetiming-fetchstart
     fn FetchStart(&self) -> DOMHighResTimeStamp {
-        Finite::wrap(self.fetch_start)
+        reduce_timing_resolution(self.fetch_start)
     }
 
     // https://w3c.github.io/resource-timing/#dom-performanceresourcetiming-connectstart
     fn ConnectStart(&self) -> DOMHighResTimeStamp {
-        Finite::wrap(self.connect_start)
+        reduce_timing_resolution(self.connect_start)
     }
 
     // https://w3c.github.io/resource-timing/#dom-performanceresourcetiming-connectend
     fn ConnectEnd(&self) -> DOMHighResTimeStamp {
-        Finite::wrap(self.connect_end)
+        reduce_timing_resolution(self.connect_end)
     }
 
     // https://w3c.github.io/resource-timing/#dom-performanceresourcetiming-responseend
     fn ResponseEnd(&self) -> DOMHighResTimeStamp {
-        Finite::wrap(self.response_end)
+        reduce_timing_resolution(self.response_end)
     }
 }

components/script/dom/vrframedata.rs

@@ -2,13 +2,14 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
+use crate::dom::bindings::codegen::Bindings::PerformanceBinding::DOMHighResTimeStamp;
 use crate::dom::bindings::codegen::Bindings::VRFrameDataBinding;
 use crate::dom::bindings::codegen::Bindings::VRFrameDataBinding::VRFrameDataMethods;
 use crate::dom::bindings::error::Fallible;
-use crate::dom::bindings::num::Finite;
 use crate::dom::bindings::reflector::{reflect_dom_object, DomObject, Reflector};
 use crate::dom::bindings::root::{Dom, DomRoot};
 use crate::dom::globalscope::GlobalScope;
+use crate::dom::performance::reduce_timing_resolution;
 use crate::dom::vrpose::VRPose;
 use crate::dom::window::Window;
 use crate::script_runtime::JSContext;
@@ -119,8 +120,8 @@ impl VRFrameData {
 
 impl VRFrameDataMethods for VRFrameData {
     // https://w3c.github.io/webvr/#dom-vrframedata-timestamp
-    fn Timestamp(&self) -> Finite<f64> {
-        Finite::wrap(self.timestamp.get() - self.first_timestamp.get())
+    fn Timestamp(&self) -> DOMHighResTimeStamp {
+        reduce_timing_resolution(self.timestamp.get() - self.first_timestamp.get())
     }
 
     #[allow(unsafe_code)]

components/script/dom/xrsession.rs

@@ -19,7 +19,6 @@ use crate::dom::bindings::codegen::Bindings::XRSessionBinding::XRVisibilityState
 use crate::dom::bindings::codegen::Bindings::XRWebGLLayerBinding::XRWebGLLayerMethods;
 use crate::dom::bindings::error::{Error, ErrorResult};
 use crate::dom::bindings::inheritance::Castable;
-use crate::dom::bindings::num::Finite;
 use crate::dom::bindings::refcounted::Trusted;
 use crate::dom::bindings::reflector::{reflect_dom_object, DomObject};
 use crate::dom::bindings::root::{Dom, DomRoot, MutDom, MutNullableDom};
@@ -28,6 +27,7 @@ use crate::dom::eventtarget::EventTarget;
 use crate::dom::globalscope::GlobalScope;
 use crate::dom::node::Node;
 use crate::dom::node::NodeDamage;
+use crate::dom::performance::reduce_timing_resolution;
 use crate::dom::promise::Promise;
 use crate::dom::xrframe::XRFrame;
 use crate::dom::xrinputsourcearray::XRInputSourceArray;
@@ -336,7 +336,7 @@ impl XRSession {
         // Step 4-5
         let mut callbacks = mem::replace(&mut *self.raf_callback_list.borrow_mut(), vec![]);
         let start = self.global().as_window().get_navigation_start();
-        let time = (frame.time_ns - start).to_ms();
+        let time = reduce_timing_resolution((frame.time_ns - start).to_ms());
 
         let frame = XRFrame::new(&self.global(), self, frame);
         // Step 6,7
@@ -347,7 +347,7 @@ impl XRSession {
         self.outside_raf.set(false);
         for (_, callback) in callbacks.drain(..) {
             if let Some(callback) = callback {
-                let _ = callback.Call__(Finite::wrap(time), &frame, ExceptionHandling::Report);
+                let _ = callback.Call__(time, &frame, ExceptionHandling::Report);
             }
         }
         self.outside_raf.set(true);

tests/wpt/metadata/dom/events/Event-timestamp-safe-resolution.html.ini

@@ -1,6 +0,0 @@
-[Event-timestamp-safe-resolution.html]
-  type: testharness
-
-  [Event timestamp should not have a resolution better than 5 microseconds]
-    expected: FAIL
-

tests/wpt/metadata/performance-timeline/webtiming-resolution.any.js.ini

@@ -1,15 +0,0 @@
-[webtiming-resolution.any.html]
-  [Verifies the resolution of performance.now() is at least 5 microseconds.]
-    expected: FAIL
-
-
-[webtiming-resolution.any.worker.html]
-  [Verifies the resolution of performance.now() is at least 20 microseconds.]
-    expected: FAIL
-
-  [Verifies the resolution of entry.startTime is at least 20 microseconds.]
-    expected: TIMEOUT
-
-  [Verifies the resolution of performance.now() is at least 5 microseconds.]
-    expected: FAIL
-

tests/wpt/mozilla/meta/MANIFEST.json

@@ -19708,7 +19708,7 @@
    "testharness"
   ],
   "mozilla/window_performance.html": [
-   "302073e8041763102d678326509d7ef0a1fb5c79",
+   "c1e38a1e00147caf82492dc82f1cb5e85759f8e3",
    "testharness"
   ],
   "mozilla/window_performance_topLevelDomComplete.html": [

tests/wpt/mozilla/tests/mozilla/window_performance.html

@@ -27,12 +27,15 @@ test(function() {
   var last = window.performance.now();
   assert_greater_than(last, 0);
 
-  // Check that window.performance.now() is monotonically increasing
+  // Check that window.performance.now() is monotonically nondecreasing
+  // and eventually increases
+  var before_loop = window.performance.now();
   for (var i = 0; i < 100; i++) {
     var next = window.performance.now();
-    assert_greater_than(next, last);
+    assert_greater_than_equal(next, last);
     last = next;
   }
+  assert_greater_than(last, before_loop, "If this fails, either performance timing is broken, or Servo JS execution has gotten much faster since this test was written.");
 });
 </script>
 </body>