Pulls display related changes from mojo to chrome

mojo/services/view_manager/focus_controller.cc

+// 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 "mojo/services/view_manager/focus_controller.h"
+
+#include "mojo/services/view_manager/focus_controller_delegate.h"
+#include "mojo/services/view_manager/server_view.h"
+#include "mojo/services/view_manager/server_view_drawn_tracker.h"
+
+namespace view_manager {
+
+FocusController::FocusController(FocusControllerDelegate* delegate,
+                                 ServerView* root)
+    : delegate_(delegate), root_(root) {
+}
+
+FocusController::~FocusController() {
+}
+
+void FocusController::SetFocusedView(ServerView* view) {
+  if (GetFocusedView() == view)
+    return;
+
+  SetFocusedViewImpl(view, CHANGE_SOURCE_EXPLICIT);
+}
+
+ServerView* FocusController::GetFocusedView() {
+  return drawn_tracker_ ? drawn_tracker_->view() : nullptr;
+}
+
+void FocusController::SetFocusedViewImpl(ServerView* view,
+                                         ChangeSource change_source) {
+  ServerView* old = GetFocusedView();
+
+  DCHECK(!view || view->IsDrawn(root_));
+
+  if (view)
+    drawn_tracker_.reset(new ServerViewDrawnTracker(root_, view, this));
+  else
+    drawn_tracker_.reset();
+
+  if (change_source == CHANGE_SOURCE_DRAWN_STATE_CHANGED)
+    delegate_->OnFocusChanged(old, view);
+}
+
+void FocusController::OnDrawnStateChanged(ServerView* ancestor,
+                                          ServerView* view,
+                                          bool is_drawn) {
+  DCHECK(!is_drawn);  // We only observe when drawn.
+  SetFocusedViewImpl(ancestor, CHANGE_SOURCE_DRAWN_STATE_CHANGED);
+}
+
+}  // namespace view_manager