Bug 1605046 - Ensure that only the Browser Toolbox iterate over process targets in the debugger. r=jdescottes

Differential Revision: https://phabricator.services.mozilla.com/D57809

--HG--
extra : moz-landing-system : lando

devtools/client/debugger/src/client/firefox/events.js

@@ -41,7 +41,7 @@ function addThreadEventListeners(thread: ThreadFront) {
 }
 
 function attachAllTargets(currentTarget: Target) {
-  return prefs.fission && currentTarget.chrome && !currentTarget.isAddon;
+  return prefs.fission && currentTarget.isParentProcess;
 }
 
 function setupEvents(dependencies: Dependencies) {

devtools/client/debugger/src/client/firefox/types.js

@@ -201,7 +201,7 @@ export type Target = {
   traits: Object,
   chrome: Boolean,
   url: string,
-  isAddon: Boolean,
+  isParentProcess: Boolean,
   isServiceWorker: boolean,
 
   // Property installed by the debugger itself.

devtools/client/debugger/test/mochitest/browser_dbg-browser-content-toolbox.js

@@ -30,9 +30,6 @@ async function enableBreakpoint(dbg, index) {
 }
 
 add_task(async function() {
-  // Disable Multiprocess Browser Toolbox for now as it introduces exceptions
-  await pushPref("devtools.browsertoolbox.fission", false);
-
   clearDebuggerPreferences();
 
   info("Open a tab pointing to doc-scripts.html");