CrOS shelf: tentative fix for unresponsive shelf

Extend the shelf hover area to the edges of the screen.

Bug: 899007
Change-Id: I344e80c9c2272ec70d5c638646bd9d5f0086f87a
Reviewed-on: https://chromium-review.googlesource.com/c/1318799Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Commit-Queue: Manu Cornet <manucornet@chromium.org>
Cr-Commit-Position: refs/heads/master@{#605714}

ash/shelf/shelf_layout_manager.cc

@@ -961,7 +961,8 @@ gfx::Rect ShelfLayoutManager::GetAutoHideShowShelfRegionInScreen() const {
 
   // TODO(pkotwicz): Figure out if we need any special handling when the
   // keyboard is visible.
-  return show_shelf_region_in_screen;
+  return screen_util::SnapBoundsToDisplayEdge(show_shelf_region_in_screen,
+                                              shelf_widget_->GetNativeWindow());
 }
 
 bool ShelfLayoutManager::HasVisibleWindow() const {