ash: Start/stop observing KeyboardController via ShellObserver

ash/root_window_controller.cc

Index: ash/root_window_controller.cc
diff --git a/ash/root_window_controller.cc b/ash/root_window_controller.cc
index 87b54b4cbf33f33bf10761afdffb2924e751f28a..14bc7c34c54a088eff1c36714bcfea2004129c82 100644
--- a/ash/root_window_controller.cc
+++ b/ash/root_window_controller.cc
@@ -673,12 +673,14 @@ void RootWindowController::ActivateKeyboard(
     return;
   }
   DCHECK(keyboard_controller);
-  keyboard_controller->AddObserver(wm_shelf_->shelf_layout_manager());
-  keyboard_controller->AddObserver(panel_layout_manager());
-  keyboard_controller->AddObserver(docked_window_layout_manager());
-  keyboard_controller->AddObserver(workspace_controller()->layout_manager());
-  keyboard_controller->AddObserver(
-      always_on_top_controller_->GetLayoutManager());
+  wm_shelf_->shelf_layout_manager()->StartObservingKeyboard(

[sky, 2017/03/10 23:40:47]

The sources an object needs to observe are generally an implementation detail of
the object. I would expect all these classes to handle adding/removing observers
as necessary rather than RootWindowController having to take care of it. WDYT of
adding ShellObserver functions for when the keyboard is activated/deactivated?
That way these classes can take care of registration themselves?

[xiyuan, 2017/03/10 23:44:11]

Yep, think it makes more sense than exiting code. Let me give it a try and ping
back.

+      keyboard_controller);
+  panel_layout_manager()->StartObservingKeyboard(keyboard_controller);
+  docked_window_layout_manager()->StartObservingKeyboard(keyboard_controller);
+  workspace_controller()->layout_manager()->StartObservingKeyboard(
+      keyboard_controller);
+  always_on_top_controller_->GetLayoutManager()->StartObservingKeyboard(
+      keyboard_controller);
   Shell::GetInstance()->NotifyVirtualKeyboardActivated(true);
   aura::Window* parent = GetContainer(kShellWindowId_ImeWindowParentContainer);
   DCHECK(parent);
@@ -703,13 +705,17 @@ void RootWindowController::DeactivateKeyboard(
     keyboard_controller->HideKeyboard(
         keyboard::KeyboardController::HIDE_REASON_AUTOMATIC);
     parent->RemoveChild(keyboard_container);
-    keyboard_controller->RemoveObserver(wm_shelf_->shelf_layout_manager());
-    keyboard_controller->RemoveObserver(panel_layout_manager());
-    keyboard_controller->RemoveObserver(docked_window_layout_manager());
-    keyboard_controller->RemoveObserver(
-        workspace_controller()->layout_manager());
-    keyboard_controller->RemoveObserver(
-        always_on_top_controller_->GetLayoutManager());
+    wm_shelf_->shelf_layout_manager()->StopObservingKeyboard(
+        keyboard_controller);
+    panel_layout_manager()->StopObservingKeyboard(keyboard_controller);
+    docked_window_layout_manager()->StopObservingKeyboard(keyboard_controller);
+    // |workspace_controller_| could be released in MoveWindowsTo.
+    if (workspace_controller()) {
+      workspace_controller()->layout_manager()->StopObservingKeyboard(
+          keyboard_controller);
+    }
+    always_on_top_controller_->GetLayoutManager()->StopObservingKeyboard(
+        keyboard_controller);
     Shell::GetInstance()->NotifyVirtualKeyboardActivated(false);
   }
 }