Bug 1916766 - Centralise HiddenBrowserManager into HiddenFrame.sys.mjs and make it a singleton. r=mossop

Differential Revision: https://phabricator.services.mozilla.com/D221061

browser/components/pagedata/PageDataService.sys.mjs

@@ -10,7 +10,7 @@ const lazy = {};
 
 ChromeUtils.defineESModuleGetters(lazy, {
   BrowserWindowTracker: "resource:///modules/BrowserWindowTracker.sys.mjs",
-  HiddenFrame: "resource://gre/modules/HiddenFrame.sys.mjs",
+  HiddenBrowserManager: "resource://gre/modules/HiddenFrame.sys.mjs",
 });
 
 ChromeUtils.defineLazyGetter(lazy, "logConsole", function () {
@@ -35,9 +35,6 @@ XPCOMUtils.defineLazyPreferenceGetter(
 
 const ALLOWED_SCHEMES = ["http", "https", "data", "blob"];
 
-const BACKGROUND_WIDTH = 1024;
-const BACKGROUND_HEIGHT = 768;
-
 /**
  * Shifts the first element out of the set.
  *
@@ -58,90 +55,6 @@ function shift(set) {
   return value;
 }
 
-/**
- * A manager for hidden browsers. Responsible for creating and destroying a
- * hidden frame to hold them.
- */
-class HiddenBrowserManager {
-  /**
-   * The hidden frame if one has been created.
-   *
-   * @type {HiddenFrame | null}
-   */
-  #frame = null;
-  /**
-   * The number of hidden browser elements currently in use.
-   *
-   * @type {number}
-   */
-  #browsers = 0;
-
-  /**
-   * Creates and returns a new hidden browser.
-   *
-   * @returns {Browser}
-   */
-  async #acquireBrowser() {
-    this.#browsers++;
-    if (!this.#frame) {
-      this.#frame = new lazy.HiddenFrame();
-    }
-
-    let frame = await this.#frame.get();
-    let doc = frame.document;
-    let browser = doc.createXULElement("browser");
-    browser.setAttribute("remote", "true");
-    browser.setAttribute("type", "content");
-    browser.setAttribute(
-      "style",
-      `
-        width: ${BACKGROUND_WIDTH}px;
-        min-width: ${BACKGROUND_WIDTH}px;
-        height: ${BACKGROUND_HEIGHT}px;
-        min-height: ${BACKGROUND_HEIGHT}px;
-      `
-    );
-    browser.setAttribute("maychangeremoteness", "true");
-    doc.documentElement.appendChild(browser);
-
-    return browser;
-  }
-
-  /**
-   * Releases the given hidden browser.
-   *
-   * @param {Browser} browser
-   *   The hidden browser element.
-   */
-  #releaseBrowser(browser) {
-    browser.remove();
-
-    this.#browsers--;
-    if (this.#browsers == 0) {
-      this.#frame.destroy();
-      this.#frame = null;
-    }
-  }
-
-  /**
-   * Calls a callback function with a new hidden browser.
-   * This function will return whatever the callback function returns.
-   *
-   * @param {Callback} callback
-   *   The callback function will be called with the browser element and may
-   *   be asynchronous.
-   * @returns {T}
-   */
-  async withHiddenBrowser(callback) {
-    let browser = await this.#acquireBrowser();
-    try {
-      return await callback(browser);
-    } finally {
-      this.#releaseBrowser(browser);
-    }
-  }
-}
-
 /**
  * @typedef {object} CacheEntry
  *   An entry in the page data cache.
@@ -293,13 +206,6 @@ export const PageDataService = new (class PageDataService extends EventEmitter {
    */
   #userIsIdle = false;
 
-  /**
-   * A manager for hidden browsers.
-   *
-   * @type {HiddenBrowserManager}
-   */
-  #browserManager = new HiddenBrowserManager();
-
   /**
    * A map of hidden browsers to a resolve function that should be passed the
    * actor that was created for the browser.
@@ -535,7 +441,7 @@ export const PageDataService = new (class PageDataService extends EventEmitter {
    *   Resolves to the found pagedata or null in case of error.
    */
   async fetchPageData(url) {
-    return this.#browserManager.withHiddenBrowser(async browser => {
+    return lazy.HiddenBrowserManager.withHiddenBrowser(async browser => {
       try {
         let { promise, resolve } = Promise.withResolvers();
         this.#backgroundBrowsers.set(browser, resolve);

toolkit/components/resistfingerprinting/UserCharacteristicsPageService.sys.mjs

@@ -6,7 +6,7 @@
 const lazy = {};
 
 ChromeUtils.defineESModuleGetters(lazy, {
-  HiddenFrame: "resource://gre/modules/HiddenFrame.sys.mjs",
+  HiddenBrowserManager: "resource://gre/modules/HiddenFrame.sys.mjs",
   Preferences: "resource://gre/modules/Preferences.sys.mjs",
   setTimeout: "resource://gre/modules/Timer.sys.mjs",
   clearTimeout: "resource://gre/modules/Timer.sys.mjs",
@@ -27,94 +27,6 @@ ChromeUtils.defineLazyGetter(lazy, "contentPrefs", () => {
   );
 });
 
-const BACKGROUND_WIDTH = 1024;
-const BACKGROUND_HEIGHT = 768;
-
-/**
- * A manager for hidden browsers. Responsible for creating and destroying a
- * hidden frame to hold them.
- * All of this is copied from PageDataService.sys.mjs
- */
-class HiddenBrowserManager {
-  /**
-   * The hidden frame if one has been created.
-   *
-   * @type {HiddenFrame | null}
-   */
-  #frame = null;
-  /**
-   * The number of hidden browser elements currently in use.
-   *
-   * @type {number}
-   */
-  #browsers = 0;
-
-  /**
-   * Creates and returns a new hidden browser.
-   *
-   * @returns {Browser}
-   */
-  async #acquireBrowser() {
-    this.#browsers++;
-    if (!this.#frame) {
-      this.#frame = new lazy.HiddenFrame();
-    }
-
-    let frame = await this.#frame.get();
-    let doc = frame.document;
-    let browser = doc.createXULElement("browser");
-    browser.setAttribute("remote", "true");
-    browser.setAttribute("type", "content");
-    browser.setAttribute(
-      "style",
-      `
-        width: ${BACKGROUND_WIDTH}px;
-        min-width: ${BACKGROUND_WIDTH}px;
-        height: ${BACKGROUND_HEIGHT}px;
-        min-height: ${BACKGROUND_HEIGHT}px;
-      `
-    );
-    browser.setAttribute("maychangeremoteness", "true");
-    doc.documentElement.appendChild(browser);
-
-    return browser;
-  }
-
-  /**
-   * Releases the given hidden browser.
-   *
-   * @param {Browser} browser
-   *   The hidden browser element.
-   */
-  #releaseBrowser(browser) {
-    browser.remove();
-
-    this.#browsers--;
-    if (this.#browsers == 0) {
-      this.#frame.destroy();
-      this.#frame = null;
-    }
-  }
-
-  /**
-   * Calls a callback function with a new hidden browser.
-   * This function will return whatever the callback function returns.
-   *
-   * @param {Callback} callback
-   *   The callback function will be called with the browser element and may
-   *   be asynchronous.
-   * @returns {T}
-   */
-  async withHiddenBrowser(callback) {
-    let browser = await this.#acquireBrowser();
-    try {
-      return await callback(browser);
-    } finally {
-      this.#releaseBrowser(browser);
-    }
-  }
-}
-
 export class UserCharacteristicsPageService {
   classId = Components.ID("{ce3e9659-e311-49fb-b18b-7f27c6659b23}");
   QueryInterface = ChromeUtils.generateQI([
@@ -124,13 +36,6 @@ export class UserCharacteristicsPageService {
   _initialized = false;
   _isParentProcess = false;
 
-  /**
-   * A manager for hidden browsers.
-   *
-   * @type {HiddenBrowserManager}
-   */
-  _browserManager = new HiddenBrowserManager();
-
   /**
    * A map of hidden browsers to a resolve function that should be passed the
    * actor that was created for the browser.
@@ -178,7 +83,7 @@ export class UserCharacteristicsPageService {
       remoteTypes: ["privilegedabout"],
     });
 
-    return this._browserManager.withHiddenBrowser(async browser => {
+    return lazy.HiddenBrowserManager.withHiddenBrowser(async browser => {
       lazy.console.debug(`In withHiddenBrowser`);
       try {
         let { promise, resolve } = Promise.withResolvers();

toolkit/modules/HiddenFrame.sys.mjs

@@ -2,10 +2,21 @@
  * 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/. */
 
+/**
+ * This module contains `HiddenFrame`, a class which creates a windowless browser,
+ * and `HiddenBrowserManager` which is a singleton that can be used to manage
+ * creating and using multiple hidden frames.
+ */
+
 const XUL_PAGE = Services.io.newURI("chrome://global/content/win.xhtml");
 
 const gAllHiddenFrames = new Set();
 
+// The screen sizes to use for the background browser created by
+// `HiddenBrowserManager`.
+const BACKGROUND_WIDTH = 1024;
+const BACKGROUND_HEIGHT = 768;
+
 let cleanupRegistered = false;
 function ensureCleanupRegistered() {
   if (!cleanupRegistered) {
@@ -121,3 +132,87 @@ export class HiddenFrame {
     this.#browser.loadURI(XUL_PAGE, loadURIOptions);
   }
 }
+
+/**
+ * A manager for hidden browsers. Responsible for creating and destroying a
+ * hidden frame to hold them.
+ */
+export const HiddenBrowserManager = new (class HiddenBrowserManager {
+  /**
+   * The hidden frame if one has been created.
+   *
+   * @type {HiddenFrame | null}
+   */
+  #frame = null;
+  /**
+   * The number of hidden browser elements currently in use.
+   *
+   * @type {number}
+   */
+  #browsers = 0;
+
+  /**
+   * Creates and returns a new hidden browser.
+   *
+   * @returns {Browser}
+   */
+  async #acquireBrowser() {
+    this.#browsers++;
+    if (!this.#frame) {
+      this.#frame = new HiddenFrame();
+    }
+
+    let frame = await this.#frame.get();
+    let doc = frame.document;
+    let browser = doc.createXULElement("browser");
+    browser.setAttribute("remote", "true");
+    browser.setAttribute("type", "content");
+    browser.setAttribute(
+      "style",
+      `
+        width: ${BACKGROUND_WIDTH}px;
+        min-width: ${BACKGROUND_WIDTH}px;
+        height: ${BACKGROUND_HEIGHT}px;
+        min-height: ${BACKGROUND_HEIGHT}px;
+      `
+    );
+    browser.setAttribute("maychangeremoteness", "true");
+    doc.documentElement.appendChild(browser);
+
+    return browser;
+  }
+
+  /**
+   * Releases the given hidden browser.
+   *
+   * @param {Browser} browser
+   *   The hidden browser element.
+   */
+  #releaseBrowser(browser) {
+    browser.remove();
+
+    this.#browsers--;
+    if (this.#browsers == 0) {
+      this.#frame.destroy();
+      this.#frame = null;
+    }
+  }
+
+  /**
+   * Calls a callback function with a new hidden browser.
+   * This function will return whatever the callback function returns.
+   *
+   * @param {Callback} callback
+   *   The callback function will be called with the browser element and may
+   *   be asynchronous.
+   * @returns {T}
+   */
+  async withHiddenBrowser(callback) {
+    let browser = await this.#acquireBrowser();
+    try {
+      return await callback(browser);
+    } finally {
+      this.#releaseBrowser(browser);
+    }
+  }
+})();