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

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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] `./mach test-tidy` does not report any errors
- [X] These changes fix #25656 fix #25296 fix #21276

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- [X] There are tests for these changes

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This commit is contained in:
bors-servo 2020-02-10 13:50:42 -05:00 • committed by GitHub
commit c0ee7594c2
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10 changed files with 46 additions and 51 deletions
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6
tests/wpt/metadata/dom/events/Event-timestamp-safe-resolution.html.ini
View file

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

15
tests/wpt/metadata/performance-timeline/webtiming-resolution.any.js.ini
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@ -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

2
tests/wpt/mozilla/meta/MANIFEST.json
View file

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

7
tests/wpt/mozilla/tests/mozilla/window_performance.html
View file

@ -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>