[WebEngine] Fix context for Toast in fullscreen mode

Change-Id: Iad6538eddf5026dae35c3a3f46116374dd565c68
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4307252
Commit-Queue: Susanne Westphal <swestphal@chromium.org>
Reviewed-by: Rayan Kanso <rayankans@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1113913}

weblayer/browser/java/org/chromium/weblayer_private/FullscreenToast.java

@@ -96,7 +96,9 @@ private void showToast() {
         assert mToast == null;
         mDidShowToast = true;
         int resId = R.string.immersive_fullscreen_api_notification;
-        mToast = Toast.makeText(mView.getContext(), resId, Toast.LENGTH_LONG);
+        mToast = Toast.makeText(
+                mTab.getBrowser().getBrowserFragment().getWindowAndroid().getContext().get(), resId,
+                Toast.LENGTH_LONG);
         mToast.setGravity(Gravity.TOP | Gravity.CENTER, 0, 0);
         mToast.show();
     }