[Refactor] Replace kFullscreenUsesMinimalChromeKey with WindowState::hide_shelf_when_fullscreen()

ash/wm/window_state.cc

Index: ash/wm/window_state.cc
diff --git a/ash/wm/window_state.cc b/ash/wm/window_state.cc
index 1aade08d89d2feb9c3df9cb3be9502711279c64e..d037a76c5588ed9b09530a388f4e63a7ea32c376 100644
--- a/ash/wm/window_state.cc
+++ b/ash/wm/window_state.cc
@@ -38,6 +38,7 @@ WindowState::WindowState(aura::Window* window)
       top_row_keys_are_function_keys_(false),
       window_resizer_(NULL),
       always_restores_to_restore_bounds_(false),
+      hide_shelf_when_fullscreen_(true),
       window_show_type_(ToWindowShowType(GetShowState())) {
   window_->AddObserver(this);
 }