Fix brave/brave-ios#8661: Always allow WebKit to load popup URLs befo…

…re switching tabs (brave/brave-ios#8683)

There was a race condition on older devices that where WebKit would not load the popup URL before Brave attempted to select the tab. Selecting the tab would then attempt to restore it using the tab's current URL which would be `about:blank` since the web view had not made any requests yet.

Sources/Brave/Frontend/Browser/BrowserViewController/BVC+WKNavigationDelegate.swift

@@ -1016,6 +1016,16 @@ extension BrowserViewController: WKUIDelegate {
     newTab.url = URL(string: "about:blank")
 
     toolbarVisibilityViewModel.toolbarState = .expanded
+
+    // Wait until WebKit starts the request before selecting the new tab, otherwise the tab manager may
+    // restore it as if it was a dead tab.
+    var observation: NSKeyValueObservation?
+    observation = newTab.webView?.observe(\.url, changeHandler: { [weak self] webView, _ in
+      _ = observation // Silence write but not read warning
+      observation = nil
+      guard let self = self, let tab = self.tabManager[webView] else { return }
+      self.tabManager.selectTab(tab)
+    })
 
     return newTab.webView
   }

Sources/Brave/Frontend/Browser/TabManager.swift

@@ -411,14 +411,6 @@ class TabManager: NSObject {
   @MainActor func addPopupForParentTab(_ parentTab: Tab, configuration: WKWebViewConfiguration) -> Tab {
     let popup = Tab(configuration: configuration, id: UUID(), type: parentTab.type, tabGeneratorAPI: tabGeneratorAPI)
     configureTab(popup, request: nil, afterTab: parentTab, flushToDisk: true, zombie: false, isPopup: true)
-
-    // Wait momentarily before selecting the new tab, otherwise the parent tab
-    // may be unable to set `window.location` on the popup immediately after
-    // calling `window.open("")`.
-    DispatchQueue.main.asyncAfter(deadline: .now() + .milliseconds(100)) {
-      self.selectTab(popup)
-    }
-
     return popup
   }