1 files changed, 10 insertions, 1 deletions
diff --git a/dom/base/test/fullscreen/test_fullscreen_modal.html b/dom/base/test/fullscreen/test_fullscreen_modal.html
index 78e70d9052..fef4e3867d 100644
--- a/dom/base/test/fullscreen/test_fullscreen_modal.html
+++ b/dom/base/test/fullscreen/test_fullscreen_modal.html
@@ -21,7 +21,7 @@ const button = document.querySelector("button");
 let clickCount = 0;
 let lastFullscreenPromise = null;
 let shouldEnterFullscreen = false;
-button.addEventListener("click", function(e) {
+button.addEventListener("click", function() {
   clickCount++;
   if (shouldEnterFullscreen) {
     const fullscreenElement = document.getElementById("fullscreen");
@@ -58,6 +58,15 @@ async function testFullscreenIsModal(modal) {
   ok(document.fullscreenElement.matches(":fullscreen"), "Fullscreen element matches :fullscreen");
   is(document.fullscreenElement.matches(":modal"), modal, "Fullscreen element matches :modal");
 
+  // Before exiting fullscreen, wait on the document becoming active,
+  // which signifies that the fullscreen request has been completely
+  // processed. It is important that the fullscreen request is all
+  // the way done, or the exit fullscreen request could be dropped.
+  let documentWrapper = SpecialPowers.wrap(document);
+  await SimpleTest.promiseWaitForCondition(() => documentWrapper.isActive(),
+                                           "Timed out waiting for document to become active.");
+  ok(documentWrapper.isActive(), "Document is active.");
+
   await document.exitFullscreen();
   clickButton(/* expectEvent = */ true);
 }