ARC: Avoid duplicate observers in IME service

components/arc/ime/arc_ime_service.cc

 // Copyright 2016 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 "components/arc/ime/arc_ime_service.h"
 
 #include <utility>
 
 #include "base/logging.h"
 #include "base/strings/utf_string_conversions.h"
@@ skipping 24 matching lines @@
 }  // namespace
 
 ////////////////////////////////////////////////////////////////////////////////
 // ArcImeService main implementation:
 
 ArcImeService::ArcImeService(ArcBridgeService* bridge_service)
     : ArcService(bridge_service),
       ime_bridge_(new ArcImeBridgeImpl(this, bridge_service)),
       ime_type_(ui::TEXT_INPUT_TYPE_NONE),
       has_composition_text_(false),
+      focus_client_(nullptr),
       keyboard_controller_(nullptr),
       test_input_method_(nullptr) {
   aura::Env* env = aura::Env::GetInstanceDontCreate();
   if (env)
     env->AddObserver(this);
 }
 
 ArcImeService::~ArcImeService() {
   ui::InputMethod* const input_method = GetInputMethod();
   if (input_method)
     input_method->DetachTextInputClient(this);
 
   for (aura::Window* window : arc_windows_.windows())
     window->RemoveObserver(this);
-  for (aura::Window* root : observing_root_windows_.windows())
-    aura::client::GetFocusClient(root)->RemoveObserver(this);
+  if (focus_client_)
+    focus_client_->RemoveObserver(this);
   aura::Env* env = aura::Env::GetInstanceDontCreate();
   if (env)
     env->RemoveObserver(this);
   // Removing |this| from KeyboardController.
   keyboard::KeyboardController* keyboard_controller =
       keyboard::KeyboardController::GetInstance();
   if (keyboard_controller && keyboard_controller_ == keyboard_controller) {
     keyboard_controller_->RemoveObserver(this);
   }
 }
@@ skipping 19 matching lines @@
 ////////////////////////////////////////////////////////////////////////////////
 // Overridden from aura::EnvObserver:
 
 void ArcImeService::OnWindowInitialized(aura::Window* new_window) {
   if (IsArcWindow(new_window)) {
     arc_windows_.Add(new_window);
     new_window->AddObserver(this);
   }
   keyboard::KeyboardController* keyboard_controller =
       keyboard::KeyboardController::GetInstance();
   if (keyboard_controller && keyboard_controller_ != keyboard_controller) {

[oshima, 2016/07/25 19:13:00]

does this mean that the keyboard_controller_ pointer is stale?

[Dominik Laskowski, 2016/07/25 19:54:18]

Yes, it can be stale after a call to KeyboardController::ResetInstance. Note
that this CL assumes that the Shell's FocusClient lives longer than the
ArcImeService. Otherwise, focus_client_ could be a stray pointer on destruction.

     // Registering |this| as an observer only once per KeyboardController.
     keyboard_controller_ = keyboard_controller;
     keyboard_controller_->AddObserver(this);
   }
 }
 
 void ArcImeService::OnWindowAddedToRootWindow(aura::Window* window) {
   aura::Window* root = window->GetRootWindow();
   aura::client::FocusClient* focus_client = aura::client::GetFocusClient(root);
-  if (focus_client && !observing_root_windows_.Contains(root)) {
-    focus_client->AddObserver(this);
-    observing_root_windows_.Add(root);
+  if (!focus_client)
+    return;
+
+  if (focus_client_) {
+    // Root windows share the same FocusClient in Ash.
+    DCHECK_EQ(focus_client_, focus_client);
+  } else {
+    focus_client_ = focus_client;
+    focus_client_->AddObserver(this);
   }
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 // Overridden from aura::client::FocusChangeObserver:
 
 void ArcImeService::OnWindowFocused(aura::Window* gained_focus,
                                    aura::Window* lost_focus) {
   // The Aura focus may or may not be on sub-window of the toplevel ARC++ frame.
   // To handle all cases, judge the state by always climbing up to the toplevel.
@@ skipping 218 matching lines @@
     base::i18n::TextDirection direction) {
   return false;
 }
 
 bool ArcImeService::IsTextEditCommandEnabled(
     ui::TextEditCommand command) const {
   return false;
 }
 
 }  // namespace arc