1 files changed, 122 insertions, 0 deletions
diff --git a/browser/components/resistfingerprinting/test/browser/file_workerPerformance.js b/browser/components/resistfingerprinting/test/browser/file_workerPerformance.js
new file mode 100644
index 0000000000..4533073180
--- /dev/null
+++ b/browser/components/resistfingerprinting/test/browser/file_workerPerformance.js
@@ -0,0 +1,122 @@
+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.
+  // When dealing with ms since epoch, a double's precision is on the order
+  // of 1/5 of a microsecond, so we use a value a little higher than that as
+  // our epsilon.
+  // To be clear, this error is introduced in our re-calculation of 'rounded'
+  // above in JavaScript.
+  if (Math.abs(rounded - x + expectedPrecision) < 0.0005) {
+    return true;
+  } else if (Math.abs(rounded - x) < 0.0005) {
+    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 runTimerTests(expectedPrecision) {
+  ok(
+    isRounded(performance.timeOrigin, expectedPrecision),
+    `In a worker, for reduceTimerPrecision, performance.timeOrigin is not correctly rounded: ` +
+      performance.timeOrigin
+  );
+
+  // 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) {
+  if (e.data.type === "runTimerTests") {
+    runTimerTests(e.data.precision);
+  } else {
+    ok(false, "Unknown message type");
+  }
+};