[Picture in Picture] Keep controls visible on mouse hover.

On Windows, hovering over the media controls triggers an ET_MOUSE_EXIT
MouseEvent. This is intended to only be caught when the mouse is
not within the video window bounds. On non-Windows, this is a noop.

Bug: 852131
Change-Id: I988d4483510c4eaafc9969edb26de407d77b0149
Reviewed-on: https://chromium-review.googlesource.com/1125139Reviewed-by: Mounir Lamouri <mlamouri@chromium.org>
Commit-Queue: Mounir Lamouri <mlamouri@chromium.org>
Cr-Commit-Position: refs/heads/master@{#572402}

chrome/browser/ui/views/overlay/overlay_window_views.cc

@@ -481,7 +481,11 @@ void OverlayWindowViews::OnMouseEvent(ui::MouseEvent* event) {
       break;
 
     case ui::ET_MOUSE_EXITED:
-      UpdateControlsVisibility(false);
+      // On Windows, ui::ET_MOUSE_EXITED is triggered when hovering over the
+      // media controls because of the HitTest. This check ensures the controls
+      // are visible if the mouse is still over the window.
+      if (!GetVideoBounds().Contains(event->location()))
+        UpdateControlsVisibility(false);
       break;
 
     case ui::ET_MOUSE_RELEASED: