CrOS shelf: stop tooltip timer when the mouse is elsewhere

Bug: 904231
Change-Id: I0eeb3131339da7d9c3cbeb308e7df50acd85220d
Reviewed-on: https://chromium-review.googlesource.com/c/1341648Reviewed-by: Alex Newcomer <newcomer@chromium.org>
Reviewed-by: Mitsuru Oshima <oshima@chromium.org>
Commit-Queue: Manu Cornet <manucornet@chromium.org>
Cr-Commit-Position: refs/heads/master@{#609501}

ash/shelf/shelf_tooltip_manager.cc

@@ -127,6 +127,8 @@ void ShelfTooltipManager::OnMouseEvent(ui::MouseEvent* event) {
   // The code below handles mouse move events within the shelf window.
   if (event->type() != ui::ET_MOUSE_MOVED ||
       event->target() != shelf_view_->GetWidget()->GetNativeWindow()) {
+    // Don't show delayed tooltips if the mouse is being active elsewhere.
+    timer_.Stop();
     return;
   }