Add rudimentary mash shelf functionality.

mash/wm/user_window_controller_impl.cc

Index: mash/wm/user_window_controller_impl.cc
diff --git a/mash/wm/user_window_controller_impl.cc b/mash/wm/user_window_controller_impl.cc
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--- /dev/null
+++ b/mash/wm/user_window_controller_impl.cc
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+// Copyright 2015 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 "mash/wm/user_window_controller_impl.h"
+
+#include "components/mus/public/cpp/window.h"
+#include "mash/wm/public/interfaces/container.mojom.h"
+#include "mash/wm/window_manager_application.h"
+
+namespace mash {
+namespace wm {
+
+UserWindowControllerImpl::UserWindowControllerImpl() : state_(nullptr) {}
+
+UserWindowControllerImpl::~UserWindowControllerImpl() {
+  if (state_)
+    GetUserWindowContainer()->RemoveObserver(this);
+}
+
+void UserWindowControllerImpl::Initialize(WindowManagerApplication* state) {
+  DCHECK(state);
+  DCHECK(!state_);
+  state_ = state;
+  GetUserWindowContainer()->AddObserver(this);
+}
+
+mus::Window* UserWindowControllerImpl::GetUserWindowContainer() const {
+  return state_->GetWindowForContainer(mojom::CONTAINER_USER_WINDOWS);
+}
+
+void UserWindowControllerImpl::OnTreeChanging(const TreeChangeParams& params) {
+  DCHECK(state_);
+  if (user_window_observer_) {
+    mus::Window* user_window_container = GetUserWindowContainer();
+    if (params.new_parent == user_window_container)
+      user_window_observer_->OnUserWindowAdded(params.target->id());
+    else if (params.old_parent == user_window_container)
+      user_window_observer_->OnUserWindowRemoved(params.target->id());
+  }
+}
+
+void UserWindowControllerImpl::AddUserWindowObserver(
+    mash::wm::mojom::UserWindowObserverPtr observer) {
+  // TODO(msw): Support multiple observers.
+  user_window_observer_ = std::move(observer);
+
+  const mus::Window::Children& windows = GetUserWindowContainer()->children();
+  mojo::Array<uint32_t> user_windows =
+      mojo::Array<uint32_t>::New(windows.size());
+  for (size_t i = 0; i < windows.size(); ++i)
+    user_windows[i] = windows[i]->id();
+  user_window_observer_->OnUserWindowObserverAdded(std::move(user_windows));
+}
+
+void UserWindowControllerImpl::FocusUserWindow(uint32_t window_id) {
+  mus::Window* window = GetUserWindowContainer()->GetChildById(window_id);
+  if (window)
+    window->SetFocus();
+}
+
+}  // namespace wm
+}  // namespace mash