1 files changed, 63 insertions, 0 deletions
diff --git a/devtools/server/tests/chrome/framerate-helpers.js b/devtools/server/tests/chrome/framerate-helpers.js
new file mode 100644
index 0000000000..1539e8b517
--- /dev/null
+++ b/devtools/server/tests/chrome/framerate-helpers.js
@@ -0,0 +1,63 @@
+/* exported getTargetForSelectedTab, waitFor, plotFPS */
+"use strict";
+const { require } = ChromeUtils.import("resource://devtools/shared/Loader.jsm");
+const { TargetFactory } = require("devtools/client/framework/target");
+const Services = require("Services");
+
+// Always log packets when running tests.
+Services.prefs.setBoolPref("devtools.debugger.log", true);
+SimpleTest.registerCleanupFunction(function() {
+  Services.prefs.clearUserPref("devtools.debugger.log");
+});
+
+SimpleTest.waitForExplicitFinish();
+
+/**
+ * Add a new test tab in the browser and load the given url.
+ * @return Promise a promise that resolves to the new target representing
+ *         the page currently opened.
+ */
+function getTargetForSelectedTab() {
+  // Get the target and get the necessary front
+  const { gBrowser } = Services.wm.getMostRecentWindow("navigator:browser");
+  return TargetFactory.forTab(gBrowser.selectedTab);
+}
+
+function waitFor(time) {
+  return new Promise(resolve => setTimeout(resolve, time));
+}
+
+function plotFPS(ticks, interval = 100, clamp = 60) {
+  const timeline = [];
+  const totalTicks = ticks.length;
+
+  // If the refresh driver didn't get a chance to tick before the
+  // recording was stopped, assume framerate was 0.
+  if (totalTicks == 0) {
+    timeline.push({ delta: 0, value: 0 });
+    timeline.push({ delta: interval, value: 0 });
+    return timeline;
+  }
+
+  let frameCount = 0;
+  let prevTime = ticks[0];
+
+  for (let i = 1; i < totalTicks; i++) {
+    const currTime = ticks[i];
+    frameCount++;
+
+    const elapsedTime = currTime - prevTime;
+    if (elapsedTime < interval) {
+      continue;
+    }
+
+    const framerate = Math.min(1000 / (elapsedTime / frameCount), clamp);
+    timeline.push({ delta: prevTime, value: framerate });
+    timeline.push({ delta: currTime, value: framerate });
+
+    frameCount = 0;
+    prevTime = currTime;
+  }
+
+  return timeline;
+}