Bug 1703629 - Discard useless prompts. r=aklotz

Differential Revision: https://phabricator.services.mozilla.com/D111474

mobile/android/components/geckoview/GeckoViewPrompter.jsm

@@ -36,6 +36,8 @@ class GeckoViewPrompter {
         this._domWin,
       ] = GeckoViewUtils.getActiveDispatcherAndWindow();
     }
+
+    this._innerWindowId = this._domWin?.browsingContext.currentWindowContext.innerWindowId;
   }
 
   get domWin() {
@@ -95,6 +97,17 @@ class GeckoViewPrompter {
     return result;
   }
 
+  checkInnerWindow() {
+    // Checks that the innerWindow where this prompt was created still matches
+    // the current innerWindow.
+    // This checks will fail if the page navigates away, making this prompt
+    // obsolete.
+    return (
+      this._innerWindowId ===
+      this._domWin.browsingContext.currentWindowContext.innerWindowId
+    );
+  }
+
   asyncShowPromptPromise(aMsg) {
     return new Promise(resolve => {
       this.asyncShowPrompt(aMsg, resolve);
@@ -107,7 +120,12 @@ class GeckoViewPrompter {
       if (handled) {
         return;
       }
-      aCallback(response);
+      if (!this.checkInnerWindow()) {
+        // Page has navigated away, let's dismiss the prompt
+        aCallback(null);
+      } else {
+        aCallback(response);
+      }
       // This callback object is tied to the Java garbage collector because
       // it is invoked from Java. Manually release the target callback
       // here; otherwise we may hold onto resources for too long, because
@@ -118,7 +136,7 @@ class GeckoViewPrompter {
       handled = true;
     };
 
-    if (!this._dispatcher) {
+    if (!this._dispatcher || !this.checkInnerWindow()) {
       onResponse(null);
       return;
     }