Makes WorkspaceLayoutManager use ash/wm/common types

ash/shelf/shelf_layout_manager.cc

Index: ash/shelf/shelf_layout_manager.cc
diff --git a/ash/shelf/shelf_layout_manager.cc b/ash/shelf/shelf_layout_manager.cc
index 482fbb58141b87a34383da830123ebe18f7a3fc3..dbaedca904cb68cde2bd23aa83dac5979caf899d 100644
--- a/ash/shelf/shelf_layout_manager.cc
+++ b/ash/shelf/shelf_layout_manager.cc
@@ -24,7 +24,10 @@
 #include "ash/shell.h"
 #include "ash/shell_window_ids.h"
 #include "ash/system/status_area_widget.h"
+#include "ash/wm/aura/wm_window_aura.h"
 #include "ash/wm/common/window_state.h"
+#include "ash/wm/common/wm_root_window_controller.h"
+#include "ash/wm/common/wm_root_window_controller_observer.h"
 #include "ash/wm/gestures/shelf_gesture_handler.h"
 #include "ash/wm/lock_state_controller.h"
 #include "ash/wm/mru_window_tracker.h"
@@ -183,6 +186,33 @@ class ShelfLayoutManager::UpdateShelfObserver
   DISALLOW_COPY_AND_ASSIGN(UpdateShelfObserver);
 };
 
+// ShelfLayoutManager::RootWindowControllerObserverImpl ------------------------
+
+// NOTE: OnShelfAlignmentChanged() is implemented by way of

[sky, 2016/04/27 20:48:05]

This is subtle and a bit unfortunate. But I think this class will die long term,
or at least be refactored in such a way that this code can be nuked.

+// WmRootWindowControllerObserver to avoid ordering issues. The way
+// WmRootWindowControllerObserver is wired in means
+// WmRootWindowControllerObservers may be notified after ShellObservers.

[James Cook, 2016/04/27 23:24:24]

The part that I missed in thinking about this was that some other layout manager
had been converted to WmRootWindowControllerObserver, and the ordering problem
was with the ones that have moved there. Is the comment below any clearer?

NOTE: Some other layout managers also observe for OnShelfAlignmentChanged() via
WmRootWindowControllerObserver instead of via ShellObserver. There are implicit
assumptions that these layout managers run in order. In order to preserve the
ordering, OnShelfAlignmentChanged() is implemented here in terms of a
WmRootWindowControllerObserver instead of a ShellObserver. This gives us a sane
ordering (or at least ordering as we've always had it in ash).

[sky, 2016/04/27 23:33:28]

I copied what you have here.

+// By making this code use a WmRootWindowControllerObservers we get sane
+// ordering (or at least ordering as we've always had it in ash).
+class ShelfLayoutManager::RootWindowControllerObserverImpl
+    : public wm::WmRootWindowControllerObserver {
+ public:
+  explicit RootWindowControllerObserverImpl(
+      ShelfLayoutManager* shelf_layout_manager)
+      : shelf_layout_manager_(shelf_layout_manager) {}
+  ~RootWindowControllerObserverImpl() override {}
+
+  // WmRootWindowControllerObserver:
+  void OnShelfAlignmentChanged() override {
+    shelf_layout_manager_->LayoutShelf();
+  }
+
+ private:
+  ShelfLayoutManager* shelf_layout_manager_;
+
+  DISALLOW_COPY_AND_ASSIGN(RootWindowControllerObserverImpl);
+};
+
 // ShelfLayoutManager ----------------------------------------------------------
 
 ShelfLayoutManager::ShelfLayoutManager(ShelfWidget* shelf)
@@ -199,8 +229,13 @@ ShelfLayoutManager::ShelfLayoutManager(ShelfWidget* shelf)
       gesture_drag_auto_hide_state_(SHELF_AUTO_HIDE_SHOWN),
       update_shelf_observer_(NULL),
       chromevox_panel_height_(0),
-      duration_override_in_ms_(0) {
+      duration_override_in_ms_(0),
+      root_window_controller_observer_(
+          new RootWindowControllerObserverImpl(this)) {
   Shell::GetInstance()->AddShellObserver(this);
+  wm::WmWindowAura::Get(root_window_)
+      ->GetRootWindowController()
+      ->AddObserver(root_window_controller_observer_.get());
   Shell::GetInstance()->lock_state_controller()->AddObserver(this);
   aura::client::GetActivationClient(root_window_)->AddObserver(this);
   Shell::GetInstance()->session_state_delegate()->AddSessionStateObserver(this);
@@ -215,6 +250,9 @@ ShelfLayoutManager::~ShelfLayoutManager() {
   Shell::GetInstance()->lock_state_controller()->RemoveObserver(this);
   Shell::GetInstance()->
       session_state_delegate()->RemoveSessionStateObserver(this);
+  wm::WmWindowAura::Get(root_window_)
+      ->GetRootWindowController()
+      ->RemoveObserver(root_window_controller_observer_.get());
 }
 
 void ShelfLayoutManager::PrepareForShutdown() {
@@ -477,10 +515,6 @@ void ShelfLayoutManager::OnLockStateChanged(bool locked) {
   UpdateShelfVisibilityAfterLoginUIChange();
 }
 
-void ShelfLayoutManager::OnShelfAlignmentChanged(aura::Window* root_window) {
-  LayoutShelf();
-}
-
 void ShelfLayoutManager::OnShelfAutoHideBehaviorChanged(
     aura::Window* root_window) {
   UpdateVisibilityState();