Remove docked windows entirely in M59.

ash/root_window_controller.h

Index: ash/root_window_controller.h
diff --git a/ash/root_window_controller.h b/ash/root_window_controller.h
index 660b2cf8525ab570a6bee5f2c9f3fc5b20e07d5b..35cb89f1d6412f286118bd7de5a95eed5a98de50 100644
--- a/ash/root_window_controller.h
+++ b/ash/root_window_controller.h
@@ -51,7 +51,6 @@ class AnimatingWallpaperWidgetController;
 class AshTouchExplorationManager;
 class AshWindowTreeHost;
 class BootSplashScreen;
-class DockedWindowLayoutManager;
 enum class LoginStatus;
 class PanelLayoutManager;
 class ShelfLayoutManager;
@@ -162,10 +161,6 @@ class ASH_EXPORT RootWindowController : public ShellObserver {
     touch_hud_projection_ = hud;
   }
 
-  DockedWindowLayoutManager* docked_window_layout_manager() {
-    return docked_window_layout_manager_;
-  }
-
   PanelLayoutManager* panel_layout_manager() { return panel_layout_manager_; }
 
   wm::RootWindowLayoutManager* root_window_layout_manager() {
@@ -337,7 +332,6 @@ class ASH_EXPORT RootWindowController : public ShellObserver {
   aura::WindowTreeHost* window_tree_host_;
 
   // LayoutManagers are owned by the window they are installed on.
-  DockedWindowLayoutManager* docked_window_layout_manager_ = nullptr;
   PanelLayoutManager* panel_layout_manager_ = nullptr;
   wm::RootWindowLayoutManager* root_window_layout_manager_ = nullptr;