Bug 1782667 - [devtools] Start multiprocess browser toolbox when running mochitests with --jsdebugger. r=jdescottes.

Differential Revision: https://phabricator.services.mozilla.com/D153599

devtools/client/framework/browser-toolbox/Launcher.jsm

@@ -61,6 +61,8 @@ const processes = new Set();
  * @property {function} onRun - A function called when the process starts running.
  * @property {boolean} overwritePreferences - Set to force overwriting the toolbox
  *                     profile's preferences with the current set of preferences.
+ * @property {boolean} forceMultiprocess - Set to force the Browser Toolbox to be in
+ *                     multiprocess mode.
  */
 
 class BrowserToolboxLauncher extends EventEmitter {
@@ -104,7 +106,7 @@ class BrowserToolboxLauncher extends EventEmitter {
    *
    * @param {...BrowserToolboxLauncherArgs} args
    */
-  constructor({ onRun, overwritePreferences } = {}) {
+  constructor({ forceMultiprocess, onRun, overwritePreferences } = {}) {
     super();
 
     if (onRun) {
@@ -115,7 +117,7 @@ class BrowserToolboxLauncher extends EventEmitter {
     Services.obs.addObserver(this.close, "quit-application");
     this.#initServer();
     this.#initProfile(overwritePreferences);
-    this.#create();
+    this.#create({ forceMultiprocess });
 
     processes.add(this);
   }
@@ -287,8 +289,12 @@ class BrowserToolboxLauncher extends EventEmitter {
 
   /**
    * Creates and initializes the profile & process for the remote debugger.
+   *
+   * @param {Object} options
+   * @param {boolean} options.forceMultiprocess: Set to true to force the Browser Toolbox to be in
+   *                    multiprocess mode.
    */
-  #create() {
+  #create({ forceMultiprocess } = {}) {
     dumpn("Initializing chrome debugging process.");
 
     let command = Services.dirsvc.get("XREExeF", Ci.nsIFile).path;
@@ -337,6 +343,7 @@ class BrowserToolboxLauncher extends EventEmitter {
       // Will be read by the Browser Toolbox Firefox instance to update the
       // devtools.browsertoolbox.fission pref on the Browser Toolbox profile.
       MOZ_BROWSER_TOOLBOX_FISSION_PREF: isBrowserToolboxFission ? "1" : "0",
+      MOZ_BROWSER_TOOLBOX_FORCE_MULTIPROCESS: forceMultiprocess ? "1" : "0",
       // Similar, but for the WebConsole input context dropdown.
       MOZ_BROWSER_TOOLBOX_INPUT_CONTEXT: isInputContextEnabled ? "1" : "0",
       // Disable safe mode for the new process in case this was opened via the

devtools/client/framework/browser-toolbox/window.js

@@ -81,6 +81,10 @@ var connect = async function() {
     "devtools.webconsole.input.context",
     env.get("MOZ_BROWSER_TOOLBOX_INPUT_CONTEXT") === "1"
   );
+  // Similar, but for the Browser Toolbox mode
+  if (env.get("MOZ_BROWSER_TOOLBOX_FORCE_MULTIPROCESS") === "1") {
+    Services.prefs.setCharPref("devtools.browsertoolbox.scope", "everything");
+  }
 
   const port = env.get("MOZ_BROWSER_TOOLBOX_PORT");
 

devtools/startup/DevToolsStartup.jsm

@@ -919,7 +919,15 @@ DevToolsStartup.prototype = {
     // See comment within BrowserToolboxLauncher.
     // Setting it as an environment variable helps it being reused if we restart the browser via CmdOrCtrl+R
     env.set("MOZ_BROWSER_TOOLBOX_BINARY", binaryPath);
-    BrowserToolboxLauncher.init();
+
+    const browserToolboxLauncherConfig = {};
+
+    // If user passed the --jsdebugger in mochitests, we want to enable the
+    // multiprocess Browser Toolbox (by default it's parent process only)
+    if (Services.prefs.getBoolPref("devtools.testing", false)) {
+      browserToolboxLauncherConfig.forceMultiprocess = true;
+    }
+    BrowserToolboxLauncher.init(browserToolboxLauncherConfig);
 
     if (pauseOnStartup) {
       // Spin the event loop until the debugger connects.