Bug 1707823 - [devtools] Set will-navigate event listener before initializing inspector front. r=ochameau.

As the inspector front initialization is asynchronous and can take some time,
we might miss will-navigate events being emitted very early (e.g. when a new
navigation happen just after a previous one).

Differential Revision: https://phabricator.services.mozilla.com/D113481

devtools/client/inspector/inspector.js

@@ -231,9 +231,8 @@ Inspector.prototype = {
       return;
     }
 
-    await this.initInspectorFront(targetFront);
-
     targetFront.on("will-navigate", this._onBeforeNavigate);
+    await this.initInspectorFront(targetFront);
 
     await Promise.all([
       this._getCssProperties(),