Bug 1598364 - Re-register DOMWindowCreated listeners when reloading browser.xhtml. r=jdescottes

In the context of the browser toolbox, the ParentProcessTarget Actor watches
all top level window's docshells. But as it registers DOMWindowCreated/pageshow/pagehide
listeners against the docshell's window (because there is no parent chromeEventListener),
it has to ensure re-registering these listeners on navigation.

Differential Revision: https://phabricator.services.mozilla.com/D54193

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

devtools/client/framework/toolbox.js

@@ -673,6 +673,12 @@ Toolbox.prototype = {
   },
 
   _stopThreadFrontListeners: function(threadFront) {
+    // Only cleanup thread listeners if it has been attached.
+    // We may have closed the toolbox before it attached, or
+    // we may not have attached to the target at all.
+    if (!threadFront) {
+      return;
+    }
     threadFront.off("paused", this._onPausedState);
     threadFront.off("resumed", this._onResumedState);
   },

devtools/server/actors/targets/browsing-context.js

@@ -1666,6 +1666,22 @@ DebuggerProgressListener.prototype = {
       this._knownWindowIDs.delete(innerID);
       this._targetActor._windowDestroyed(window, innerID);
     }
+
+    // Bug 1598364: when debugging browser.xhtml from the Browser Toolbox
+    // the DOMWindowCreated/pageshow/pagehide event listeners have to be
+    // re-registered against the next document when we reload browser.html
+    // (or navigate to another doc).
+    // That's because we registered the listener on docShell.domWindow as
+    // top level windows don't have a chromeEventHandler.
+    if (
+      this._watchedDocShells.has(window) &&
+      !window.docShell.chromeEventHandler
+    ) {
+      // First cleanup all the existing listeners
+      this.unwatch(window.docShell);
+      // Re-register new ones. The docShell is already referencing the new document.
+      this.watch(window.docShell);
+    }
   }, "DebuggerProgressListener.prototype.observe"),
 
   onStateChange: DevToolsUtils.makeInfallible(function(