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diff --git a/devtools/client/performance-new/utils.js b/devtools/client/performance-new/utils.js
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+++ b/devtools/client/performance-new/utils.js
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+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+// @ts-check
+/**
+ * @typedef {import("./@types/perf").NumberScaler} NumberScaler
+ * @typedef {import("./@types/perf").ScaleFunctions} ScaleFunctions
+ * @typedef {import("./@types/perf").FeatureDescription} FeatureDescription
+ */
+"use strict";
+
+// @ts-ignore
+const { OS } = require("resource://gre/modules/osfile.jsm");
+
+const UNITS = ["B", "kiB", "MiB", "GiB", "TiB", "PiB", "EiB", "ZiB", "YiB"];
+
+/**
+ * Linearly interpolate between values.
+ * https://en.wikipedia.org/wiki/Linear_interpolation
+ *
+ * @param {number} frac - Value ranged 0 - 1 to interpolate between the range start and range end.
+ * @param {number} rangeStart - The value to start from.
+ * @param {number} rangeEnd - The value to interpolate to.
+ * @returns {number}
+ */
+function lerp(frac, rangeStart, rangeEnd) {
+  return (1 - frac) * rangeStart + frac * rangeEnd;
+}
+
+/**
+ * Make sure a value is clamped between a min and max value.
+ *
+ * @param {number} val - The value to clamp.
+ * @param {number} min - The minimum value.
+ * @param {number} max - The max value.
+ * @returns {number}
+ */
+function clamp(val, min, max) {
+  return Math.max(min, Math.min(max, val));
+}
+
+/**
+ * Formats a file size.
+ * @param {number} num - The number (in bytes) to format.
+ * @returns {string} e.g. "10 B", "100 MiB"
+ */
+function formatFileSize(num) {
+  if (!Number.isFinite(num)) {
+    throw new TypeError(`Expected a finite number, got ${typeof num}: ${num}`);
+  }
+
+  const neg = num < 0;
+
+  if (neg) {
+    num = -num;
+  }
+
+  if (num < 1) {
+    return (neg ? "-" : "") + num + " B";
+  }
+
+  const exponent = Math.min(
+    Math.floor(Math.log2(num) / Math.log2(1024)),
+    UNITS.length - 1
+  );
+  const numStr = Number((num / Math.pow(1024, exponent)).toPrecision(3));
+  const unit = UNITS[exponent];
+
+  return (neg ? "-" : "") + numStr + " " + unit;
+}
+
+/**
+ * Creates numbers that scale exponentially.
+ *
+ * @param {number} rangeStart
+ * @param {number} rangeEnd
+ *
+ * @returns {ScaleFunctions}
+ */
+function makeExponentialScale(rangeStart, rangeEnd) {
+  const startExp = Math.log(rangeStart);
+  const endExp = Math.log(rangeEnd);
+
+  /** @type {NumberScaler} */
+  const fromFractionToValue = frac =>
+    Math.exp((1 - frac) * startExp + frac * endExp);
+
+  /** @type {NumberScaler} */
+  const fromValueToFraction = value =>
+    (Math.log(value) - startExp) / (endExp - startExp);
+
+  /** @type {NumberScaler} */
+  const fromFractionToSingleDigitValue = frac => {
+    return +fromFractionToValue(frac).toPrecision(1);
+  };
+
+  return {
+    // Takes a number ranged 0-1 and returns it within the range.
+    fromFractionToValue,
+    // Takes a number in the range, and returns a value between 0-1
+    fromValueToFraction,
+    // Takes a number ranged 0-1 and returns a value in the range, but with
+    // a single digit value.
+    fromFractionToSingleDigitValue,
+  };
+}
+
+/**
+ * Creates numbers that scale exponentially as powers of 2.
+ *
+ * @param {number} rangeStart
+ * @param {number} rangeEnd
+ *
+ * @returns {ScaleFunctions}
+ */
+function makePowerOf2Scale(rangeStart, rangeEnd) {
+  const startExp = Math.log2(rangeStart);
+  const endExp = Math.log2(rangeEnd);
+
+  /** @type {NumberScaler} */
+  const fromFractionToValue = frac =>
+    Math.pow(2, Math.round((1 - frac) * startExp + frac * endExp));
+
+  /** @type {NumberScaler} */
+  const fromValueToFraction = value =>
+    (Math.log2(value) - startExp) / (endExp - startExp);
+
+  /** @type {NumberScaler} */
+  const fromFractionToSingleDigitValue = frac => {
+    // fromFractionToValue returns an exact power of 2, we don't want to change
+    // its precision. Note that formatFileSize will display it in a nice binary
+    // unit with up to 3 digits.
+    return fromFractionToValue(frac);
+  };
+
+  return {
+    // Takes a number ranged 0-1 and returns it within the range.
+    fromFractionToValue,
+    // Takes a number in the range, and returns a value between 0-1
+    fromValueToFraction,
+    // Takes a number ranged 0-1 and returns a value in the range, but with
+    // a single digit value.
+    fromFractionToSingleDigitValue,
+  };
+}
+
+/**
+ * Scale a source range to a destination range, but clamp it within the
+ * destination range.
+ * @param {number} val - The source range value to map to the destination range,
+ * @param {number} sourceRangeStart,
+ * @param {number} sourceRangeEnd,
+ * @param {number} destRangeStart,
+ * @param {number} destRangeEnd
+ */
+function scaleRangeWithClamping(
+  val,
+  sourceRangeStart,
+  sourceRangeEnd,
+  destRangeStart,
+  destRangeEnd
+) {
+  const frac = clamp(
+    (val - sourceRangeStart) / (sourceRangeEnd - sourceRangeStart),
+    0,
+    1
+  );
+  return lerp(frac, destRangeStart, destRangeEnd);
+}
+
+/**
+ * Use some heuristics to guess at the overhead of the recording settings.
+ *
+ * TODO - Bug 1597383. The UI for this has been removed, but it needs to be reworked
+ * for new overhead calculations. Keep it for now in tree.
+ *
+ * @param {number} interval
+ * @param {number} bufferSize
+ * @param {string[]} features - List of the selected features.
+ */
+function calculateOverhead(interval, bufferSize, features) {
+  // NOT "nostacksampling" (double negative) means periodic sampling is on.
+  const periodicSampling = !features.includes("nostacksampling");
+  const overheadFromSampling = periodicSampling
+    ? scaleRangeWithClamping(
+        Math.log(interval),
+        Math.log(0.05),
+        Math.log(1),
+        1,
+        0
+      ) +
+      scaleRangeWithClamping(
+        Math.log(interval),
+        Math.log(1),
+        Math.log(100),
+        0.1,
+        0
+      )
+    : 0;
+  const overheadFromBuffersize = scaleRangeWithClamping(
+    Math.log(bufferSize),
+    Math.log(10),
+    Math.log(1000000),
+    0,
+    0.1
+  );
+  const overheadFromStackwalk =
+    features.includes("stackwalk") && periodicSampling ? 0.05 : 0;
+  const overheadFromJavaScript =
+    features.includes("js") && periodicSampling ? 0.05 : 0;
+  const overheadFromTaskTracer = features.includes("tasktracer") ? 0.05 : 0;
+  const overheadFromJSTracer = features.includes("jstracer") ? 0.05 : 0;
+  const overheadFromJSAllocations = features.includes("jsallocations")
+    ? 0.05
+    : 0;
+  const overheadFromNativeAllocations = features.includes("nativeallocations")
+    ? 0.5
+    : 0;
+
+  return clamp(
+    overheadFromSampling +
+      overheadFromBuffersize +
+      overheadFromStackwalk +
+      overheadFromJavaScript +
+      overheadFromTaskTracer +
+      overheadFromJSTracer +
+      overheadFromJSAllocations +
+      overheadFromNativeAllocations,
+    0,
+    1
+  );
+}
+
+/**
+ * Given an array of absolute paths on the file system, return an array that
+ * doesn't contain the common prefix of the paths; in other words, if all paths
+ * share a common ancestor directory, cut off the path to that ancestor
+ * directory and only leave the path components that differ.
+ * This makes some lists look a little nicer. For example, this turns the list
+ * ["/Users/foo/code/obj-m-android-opt", "/Users/foo/code/obj-m-android-debug"]
+ * into the list ["obj-m-android-opt", "obj-m-android-debug"].
+ *
+ * @param {string[]} pathArray The array of absolute paths.
+ * @returns {string[]} A new array with the described adjustment.
+ */
+function withCommonPathPrefixRemoved(pathArray) {
+  if (pathArray.length === 0) {
+    return [];
+  }
+  const splitPaths = pathArray.map(path => OS.Path.split(path));
+  if (!splitPaths.every(sp => sp.absolute)) {
+    // We're expecting all paths to be absolute, so this is an unexpected case,
+    // return the original array.
+    return pathArray;
+  }
+  const [firstSplitPath, ...otherSplitPaths] = splitPaths;
+  if ("winDrive" in firstSplitPath) {
+    const winDrive = firstSplitPath.winDrive;
+    if (!otherSplitPaths.every(sp => sp.winDrive === winDrive)) {
+      return pathArray;
+    }
+  } else if (otherSplitPaths.some(sp => "winDrive" in sp)) {
+    // Inconsistent winDrive property presence, bail out.
+    return pathArray;
+  }
+  // At this point we're either not on Windows or all paths are on the same
+  // winDrive. And all paths are absolute.
+  // Find the common prefix. Start by assuming the entire path except for the
+  // last folder is shared.
+  const prefix = firstSplitPath.components.slice(0, -1);
+  for (const sp of otherSplitPaths) {
+    prefix.length = Math.min(prefix.length, sp.components.length - 1);
+    for (let i = 0; i < prefix.length; i++) {
+      if (prefix[i] !== sp.components[i]) {
+        prefix.length = i;
+        break;
+      }
+    }
+  }
+  if (prefix.length === 0 || (prefix.length === 1 && prefix[0] === "")) {
+    // There is no shared prefix.
+    // We treat a prefix of [""] as "no prefix", too: Absolute paths on
+    // non-Windows start with a slash, so OS.Path.split(path) always returns an
+    // array whose first element is the empty string on those platforms.
+    // Stripping off a prefix of [""] from the split paths would simply remove
+    // the leading slash from the un-split paths, which is not useful.
+    return pathArray;
+  }
+  return splitPaths.map(sp =>
+    OS.Path.join(...sp.components.slice(prefix.length))
+  );
+}
+
+class UnhandledCaseError extends Error {
+  /**
+   * @param {never} value - Check that
+   * @param {string} typeName - A friendly type name.
+   */
+  constructor(value, typeName) {
+    super(`There was an unhandled case for "${typeName}": ${value}`);
+    this.name = "UnhandledCaseError";
+  }
+}
+
+/**
+ * @type {FeatureDescription[]}
+ */
+const featureDescriptions = [
+  {
+    name: "Native Stacks",
+    value: "stackwalk",
+    title:
+      "Record native stacks (C++ and Rust). This is not available on all platforms.",
+    recommended: true,
+    disabledReason: "Native stack walking is not supported on this platform.",
+  },
+  {
+    name: "JavaScript",
+    value: "js",
+    title:
+      "Record JavaScript stack information, and interleave it with native stacks.",
+    recommended: true,
+  },
+  {
+    name: "Java",
+    value: "java",
+    title: "Profile Java code",
+    disabledReason: "This feature is only available on Android.",
+  },
+  {
+    name: "Native Leaf Stack",
+    value: "leaf",
+    title:
+      "Record the native memory address of the leaf-most stack. This could be " +
+      "useful on platforms that do not support stack walking.",
+  },
+  {
+    name: "No Periodic Sampling",
+    value: "nostacksampling",
+    title: "Disable interval-based stack sampling",
+  },
+  {
+    name: "Main Thread File IO",
+    value: "mainthreadio",
+    title: "Record main thread File I/O markers.",
+  },
+  {
+    name: "Profiled Threads File IO",
+    value: "fileio",
+    title: "Record File I/O markers from only profiled threads.",
+  },
+  {
+    name: "All File IO",
+    value: "fileioall",
+    title:
+      "Record File I/O markers from all threads, even unregistered threads.",
+  },
+  {
+    name: "No File IO Stack Sampling",
+    value: "noiostacks",
+    title: "Do not sample stacks when recording File I/O markers.",
+  },
+  {
+    name: "Sequential Styling",
+    value: "seqstyle",
+    title: "Disable parallel traversal in styling.",
+  },
+  {
+    name: "TaskTracer",
+    value: "tasktracer",
+    title: "Enable TaskTracer",
+    experimental: true,
+    disabledReason:
+      "TaskTracer requires a custom build with the environment variable MOZ_TASK_TRACER set.",
+  },
+  {
+    name: "Screenshots",
+    value: "screenshots",
+    title: "Record screenshots of all browser windows.",
+  },
+  {
+    name: "JSTracer",
+    value: "jstracer",
+    title: "Trace JS engine",
+    experimental: true,
+    disabledReason:
+      "JS Tracer is currently disabled due to crashes. See Bug 1565788.",
+  },
+  {
+    name: "Preference Read",
+    value: "preferencereads",
+    title: "Track Preference Reads",
+  },
+  {
+    name: "IPC Messages",
+    value: "ipcmessages",
+    title: "Track IPC messages.",
+  },
+  {
+    name: "JS Allocations",
+    value: "jsallocations",
+    title: "Track JavaScript allocations",
+  },
+  {
+    name: "Native Allocations",
+    value: "nativeallocations",
+    title: "Track native allocations",
+  },
+  {
+    name: "Audio Callback Tracing",
+    value: "audiocallbacktracing",
+    title: "Trace real-time audio callbacks.",
+  },
+  {
+    name: "CPU Utilization",
+    value: "cpu",
+    title:
+      "CPU utilization by threads. To view graphs, in about:config set " +
+      "devtools.performance.recording.ui-base-url to " +
+      "https://deploy-preview-3098--perf-html.netlify.app",
+    experimental: true,
+  },
+];
+
+module.exports = {
+  formatFileSize,
+  makeExponentialScale,
+  makePowerOf2Scale,
+  scaleRangeWithClamping,
+  calculateOverhead,
+  withCommonPathPrefixRemoved,
+  UnhandledCaseError,
+  featureDescriptions,
+};