Add EventRewriterController as an aura::Env observer.

chrome/browser/chromeos/events/event_rewriter_controller.cc

 // Copyright 2014 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 "chrome/browser/chromeos/events/event_rewriter_controller.h"
 
 #include "ash/shell.h"
+#include "ui/aura/env.h"
 #include "ui/aura/window_tree_host.h"
 #include "ui/events/event_source.h"
 
 namespace chromeos {
 
 EventRewriterController::EventRewriterController() : initialized_(false) {
 }
 
 EventRewriterController::~EventRewriterController() {
+  aura::Env::GetInstance()->RemoveObserver(this);
   // Remove the rewriters from every root window EventSource and destroy them.
   for (EventRewriters::iterator rewriter_iter = rewriters_.begin();
        rewriter_iter != rewriters_.end();
        ++rewriter_iter) {
     aura::Window::Windows windows = ash::Shell::GetAllRootWindows();
     for (aura::Window::Windows::iterator window_iter = windows.begin();
          window_iter != windows.end();
          ++window_iter) {
       (*window_iter)->GetHost()->GetEventSource()->RemoveEventRewriter(
           *rewriter_iter);
@@ skipping 11 matching lines @@
 void EventRewriterController::Init() {
   DCHECK(!initialized_);
   initialized_ = true;
   // Add the rewriters to each existing root window EventSource.
   aura::Window::Windows windows = ash::Shell::GetAllRootWindows();
   for (aura::Window::Windows::iterator it = windows.begin();
        it != windows.end();
        ++it) {
     AddToEventSource((*it)->GetHost()->GetEventSource());
   }
+  // Add the controller as an observer for new root windows.
+  aura::Env::GetInstance()->AddObserver(this);

[Daniel Erat, 2014/05/13 15:27:31]

can you do this in the c'tor instead? the add/remove calls are unbalanced
otherwise (e.g. creating an EventRewriterController and then destroying it
without having called Init() will result in a remove call with no corresponding
add)

 }
 
 void EventRewriterController::OnHostInitialized(aura::WindowTreeHost* host) {
   if (initialized_)
     AddToEventSource(host->GetEventSource());
 }
 
 void EventRewriterController::AddToEventSource(ui::EventSource* source) {
   DCHECK(source);
   for (EventRewriters::iterator it = rewriters_.begin(); it != rewriters_.end();
        ++it) {
     source->AddEventRewriter(*it);
   }
 }
 
 }  // namespace chromeos