Bug 1582502 - Don't interpret a click at 0,0 of a fullscreen video as…

… a click on the Picture-in-Picture toggle. r=JSON_voorhees

We weren't handling the case where the toggle has no dimensions, so its X and Y
coordinate would be at 0,0, which would match a click in the top-left corner of
the screen for a video that was fullscreened.

This adds a check that ensures that the toggle has both width and height before
checking whether or not a mouse event occurred within it.

Differential Revision: https://phabricator.services.mozilla.com/D47789

toolkit/actors/PictureInPictureChild.jsm

@@ -664,7 +664,14 @@ class PictureInPictureToggleChild extends ActorChild {
     let toggleRect = toggle.ownerGlobal.windowUtils.getBoundsWithoutFlushing(
       toggle
     );
+
+    // If the toggle has no dimensions, we're definitely not over it.
+    if (!toggleRect.width || !toggleRect.height) {
+      return false;
+    }
+
     let { clientX, clientY } = event;
+
     return (
       clientX >= toggleRect.left &&
       clientX <= toggleRect.right &&