ash: Start/stop observing KeyboardController via ShellObserver

ash/root_window_controller.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ash/root_window_controller.h"
 
 #include <algorithm>
 #include <queue>
 #include <vector>
 
@@ skipping 655 matching lines @@
       wm::GetWindowForFullscreenMode(WmWindow::Get(GetRootWindow())));
 }
 
 void RootWindowController::ActivateKeyboard(
     keyboard::KeyboardController* keyboard_controller) {
   if (!keyboard::IsKeyboardEnabled() ||
       GetContainer(kShellWindowId_VirtualKeyboardContainer)) {
     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);
   aura::Window* keyboard_container = keyboard_controller->GetContainerWindow();
   keyboard_container->set_id(kShellWindowId_VirtualKeyboardContainer);
   parent->AddChild(keyboard_container);
 }
 
 void RootWindowController::DeactivateKeyboard(
     keyboard::KeyboardController* keyboard_controller) {
   if (!keyboard_controller ||
       !keyboard_controller->keyboard_container_initialized()) {
     return;
   }
   aura::Window* keyboard_container = keyboard_controller->GetContainerWindow();
   if (keyboard_container->GetRootWindow() == GetRootWindow()) {
     aura::Window* parent =
         GetContainer(kShellWindowId_ImeWindowParentContainer);
     DCHECK(parent);
     // Virtual keyboard may be deactivated while still showing, hide the
     // keyboard before removing it from view hierarchy.
     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);
   }
 }
 
 bool RootWindowController::IsVirtualKeyboardWindow(aura::Window* window) {
   aura::Window* parent = GetContainer(kShellWindowId_ImeWindowParentContainer);
   return parent ? parent->Contains(window) : false;
 }
 
 void RootWindowController::SetTouchAccessibilityAnchorPoint(
@@ skipping 430 matching lines @@
     EnableTouchHudProjection();
   else
     DisableTouchHudProjection();
 }
 
 RootWindowController* GetRootWindowController(const aura::Window* root_window) {
   return root_window ? GetRootWindowSettings(root_window)->controller : nullptr;
 }
 
 }  // namespace ash