Bug 1430173 - Add Timer Rounding tests backported from -central to -esr. r=baku, a=RyanVM

MozReview-Commit-ID: Jl4WZAamgrI

--HG--
extra : transplant_source : E%DC%91lU%1C%A4l%2C%C8%23PCz%EB%F2%81%25%1F%90

dom/tests/browser/file_workerPerformance.js

@@ -0,0 +1,65 @@
+function ok(a, msg) {
+  postMessage({type: "status", status: !!a, msg});
+}
+
+function is(a, b, msg) {
+  ok(a === b, msg);
+}
+
+function finish() {
+  postMessage({type: "finish"});
+}
+
+let isRounded = (x, expectedPrecision) => {
+  let rounded = (Math.floor(x / expectedPrecision) * expectedPrecision);
+  // First we do the perfectly normal check that should work just fine
+  if (rounded === x || x === 0)
+    return true;
+
+  // When we're diving by non-whole numbers, we may not get perfect
+  // multiplication/division because of floating points
+  if (Math.abs(rounded - x + expectedPrecision) < .0000001) {
+    return true;
+  } else if (Math.abs(rounded - x) < .0000001) {
+    return true;
+  }
+
+  // Then we handle the case where you're sub-millisecond and the timer is not
+  // We check that the timer is not sub-millisecond by assuming it is not if it
+  // returns an even number of milliseconds
+  if (expectedPrecision < 1 && Math.round(x) == x) {
+    if (Math.round(rounded) == x) {
+      return true;
+    }
+  }
+
+  ok(false, "Looming Test Failure, Additional Debugging Info: Expected Precision: " + expectedPrecision + " Measured Value: " + x +
+    " Rounded Vaue: " + rounded + " Fuzzy1: " + Math.abs(rounded - x + expectedPrecision) +
+    " Fuzzy 2: " + Math.abs(rounded - x));
+
+  return false;
+};
+
+function runRTPTests(expectedPrecision) {
+  // Try to add some entries.
+  performance.mark("Test");
+  performance.mark("Test-End");
+  performance.measure("Test-Measure", "Test", "Test-End");
+
+  // Check the entries in performance.getEntries/getEntriesByType/getEntriesByName.
+  is(performance.getEntries().length, 3, "In a worker, for reduceTimerPrecision: Incorrect number of entries for performance.getEntries() for workers: " + performance.getEntries().length);
+  for (var i = 0; i < 3; i++) {
+    let startTime = performance.getEntries()[i].startTime;
+    let duration = performance.getEntries()[i].duration;
+    ok(isRounded(startTime, expectedPrecision), "In a worker, for reduceTimerPrecision(" + expectedPrecision + "), performance.getEntries(" + i.toString() + ").startTime is not rounded: " + startTime.toString());
+    ok(isRounded(duration, expectedPrecision), "In a worker, for reduceTimerPrecision(" + expectedPrecision + "), performance.getEntries(" + i.toString() + ").duration is not rounded: " + duration.toString());
+  }
+  is(performance.getEntriesByType("mark").length, 2, "In a worker, for reduceTimerPrecision: Incorrect number of entries for performance.getEntriesByType() for workers: " + performance.getEntriesByType("resource").length);
+  is(performance.getEntriesByName("Test", "mark").length, 1, "In a worker, for reduceTimerPrecision: Incorrect number of entries for performance.getEntriesByName() for workers: " + performance.getEntriesByName("Test", "mark").length);
+
+  finish();
+}
+
+self.onmessage = function(e) {
+  runRTPTests(e.data.precision);
+};