Upstream high resolution event timestamp test to WPT.

This is in anticipation of DOM spec patch landing [1]. Upstreaming two tests: - verify constructed events get a high-resolution time from perfomance.now() - verify the minimum resolution is larger that 5µs. [1] whatwg/dom#23 [2] whatwg/dom#420 BUG=538600 Review-Url: https://codereview.chromium.org/2744553007 Cr-Commit-Position: refs/heads/master@{#485966}
web-platform-tests · Jul 12, 2017 · 0a0c7d8 · 0a0c7d8
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diff --git a/dom/events/Event-timestamp-high-resolution.html b/dom/events/Event-timestamp-high-resolution.html
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+<!DOCTYPE html>
+
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script type="text/javascript">
+'use strict';
+for (let eventType of [MouseEvent, KeyboardEvent, WheelEvent, GamepadEvent, FocusEvent]) {
+    test(function() {
+        let before = performance.now();
+        let e = new eventType('test');
+        let after = performance.now();
+        assert_greater_than_equal(e.timeStamp, before, "Event timestamp should be greater than performance.now() timestamp taken before its creation");
+        assert_less_than_equal(e.timeStamp, after, "Event timestamp should be less than performance.now() timestamp taken after its creation");
+    }, `Constructed ${eventType.prototype.constructor.name} timestamp should be high resolution and have the same time origin as performance.now()`);
+}
+</script>
diff --git a/dom/events/Event-timestamp-safe-resolution.html b/dom/events/Event-timestamp-safe-resolution.html
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+<!DOCTYPE html>
+
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script type="text/javascript">
+'use strict';
+
+test(function() {
+    let e1 = new MouseEvent('test1');
+    let e2 = new MouseEvent('test2');
+
+    while (e1.timeStamp == e2.timeStamp)
+        e2 = new MouseEvent('test2');
+
+    let expectedResolutionMilliseconds = 0.005;
+    let integerMultipleOfResolution = (e2.timeStamp - e1.timeStamp) / expectedResolutionMilliseconds;
+    let shouldBeNearZeroOrOne = integerMultipleOfResolution % 1;
+    assert_true(shouldBeNearZeroOrOne < 1e-10 || Math.abs(shouldBeNearZeroOrOne - 1) < 1e-10);
+}, 'Event timestamp should not have a resolution better that 5 microseconds');
+</script>