CrOS shelf: update separator as needed

This fixes a bug whereby when pinning or un-pinning an app in a way
that didn't require a reorder (e.g. pinning the leftmost running app)
did not cause the separator to appear.

Bug: 877348
Change-Id: I2f509a32f69f4779806430b4c08a96268171edef
Reviewed-on: https://chromium-review.googlesource.com/1187962Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Commit-Queue: Manu Cornet <manucornet@chromium.org>
Cr-Commit-Position: refs/heads/master@{#585882}

ash/shelf/shelf_view.cc

@@ -1923,6 +1923,11 @@ void ShelfView::ShelfItemChanged(int model_index, const ShelfItem& old_item) {
       AnimateToIdealBounds();
     else
       bounds_animator_->AnimateViewTo(new_view, old_ideal_bounds);
+
+    // If an item is being pinned or unpinned, show the new status of the
+    // shelf immediately so that the separator gets drawn as needed.
+    if (old_item.type == TYPE_PINNED_APP || item.type == TYPE_PINNED_APP)
+      AnimateToIdealBounds();
     return;
   }