ash: Start/stop observing KeyboardController via ShellObserver

ash/common/wm/workspace/workspace_layout_manager.cc

Index: ash/common/wm/workspace/workspace_layout_manager.cc
diff --git a/ash/common/wm/workspace/workspace_layout_manager.cc b/ash/common/wm/workspace/workspace_layout_manager.cc
index f33abb0f1ca76828028cc2da1ba117d79d7d0189..ec1451f39658f39578ccc2d7fcae3f422f40402f 100644
--- a/ash/common/wm/workspace/workspace_layout_manager.cc
+++ b/ash/common/wm/workspace/workspace_layout_manager.cc
@@ -40,7 +40,8 @@ WorkspaceLayoutManager::WorkspaceLayoutManager(WmWindow* window)
       root_window_controller_(root_window_->GetRootWindowController()),
       shell_(window_->GetShell()),
       work_area_in_parent_(wm::GetDisplayWorkAreaBoundsInParent(window_)),
-      is_fullscreen_(wm::GetWindowForFullscreenMode(window) != nullptr) {
+      is_fullscreen_(wm::GetWindowForFullscreenMode(window) != nullptr),
+      keyboard_observer_(this) {
   Shell::GetInstance()->AddShellObserver(this);
   Shell::GetInstance()->activation_client()->AddObserver(this);
   root_window_->aura_window()->AddObserver(this);
@@ -66,6 +67,18 @@ void WorkspaceLayoutManager::SetMaximizeBackdropDelegate(
   backdrop_delegate_ = std::move(delegate);
 }
 
+void WorkspaceLayoutManager::StartObservingKeyboard(
+    keyboard::KeyboardController* keyboard_controller) {
+  DCHECK(!keyboard_observer_.IsObservingSources());
+  keyboard_observer_.Add(keyboard_controller);
+}
+
+void WorkspaceLayoutManager::StopObservingKeyboard(
+    keyboard::KeyboardController* keyboard_controller) {
+  if (keyboard_observer_.IsObserving(keyboard_controller))
+    keyboard_observer_.Remove(keyboard_controller);
+}
+
 //////////////////////////////////////////////////////////////////////////////
 // WorkspaceLayoutManager, aura::LayoutManager implementation:
 
@@ -178,7 +191,9 @@ void WorkspaceLayoutManager::OnKeyboardBoundsChanging(
   }
 }
 
-void WorkspaceLayoutManager::OnKeyboardClosed() {}
+void WorkspaceLayoutManager::OnKeyboardClosed() {
+  keyboard_observer_.RemoveAll();
+}
 
 //////////////////////////////////////////////////////////////////////////////
 // WorkspaceLayoutManager, aura::WindowObserver implementation: