Reify view ownership as a message pipe.

services/ui/view_manager/view_stub.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 "services/ui/view_manager/view_stub.h"
+
+#include "base/bind.h"
+#include "base/logging.h"
+#include "services/ui/view_manager/view_registry.h"
+#include "services/ui/view_manager/view_state.h"
+#include "services/ui/view_manager/view_tree_state.h"
+
+namespace view_manager {
+
+ViewStub::ViewStub(ViewRegistry* registry, mojo::ui::ViewOwnerPtr owner)
+    : registry_(registry), owner_(owner.Pass()) {
+  DCHECK(registry_);
+  DCHECK(owner_);
+
+  owner_.set_connection_error_handler(
+      base::Bind(&ViewStub::OnViewResolved, base::Unretained(this), nullptr));
+  owner_->GetToken(
+      base::Bind(&ViewStub::OnViewResolved, base::Unretained(this)));
+}
+
+ViewStub::~ViewStub() {
+  // Ensure that everything was properly released before this object was
+  // destroyed.  The |ViewRegistry| is responsible for maintaining the
+  // invariant that all |ViewState| objects are owned so by the time we
+  // get here, the view should have found a new owner or been unregistered.
+  DCHECK(is_unavailable());
+}
+
+void ViewStub::AttachView(ViewState* state) {
+  DCHECK(state);
+  DCHECK(!state->view_stub());
+  DCHECK(is_pending());
+
+  state_ = state;
+  state_->set_view_stub(this);
+}
+
+ViewState* ViewStub::ReleaseView() {
+  if (is_unavailable())
+    return nullptr;
+
+  ViewState* state = state_;
+  if (state) {
+    DCHECK(state->view_stub() == this);
+    state->set_view_stub(nullptr);
+    state_ = nullptr;
+  }
+  unavailable_ = true;
+  return state;
+}
+
+void ViewStub::SetTree(ViewTreeState* tree, uint32_t key) {
+  DCHECK(tree);
+  DCHECK(!tree_ && !parent_);
+
+  key_ = key;
+  SetTreeRecursively(tree);
+}
+
+void ViewStub::SetParent(ViewState* parent, uint32_t key) {
+  DCHECK(parent);
+  DCHECK(!tree_ && !parent_);
+
+  parent_ = parent;
+  key_ = key;
+  if (parent->view_stub())
+    SetTreeRecursively(parent->view_stub()->tree());
+}
+
+void ViewStub::Unlink() {
+  parent_ = nullptr;
+  key_ = 0;
+  SetTreeRecursively(nullptr);
+}
+
+void ViewStub::SetTreeRecursively(ViewTreeState* tree) {
+  if (tree_ == tree)
+    return;
+  tree_ = tree;
+  if (state_) {
+    for (const auto& pair : state_->children()) {
+      pair.second->SetTreeRecursively(tree);
+    }
+  }
+}
+
+void ViewStub::OnViewResolved(mojo::ui::ViewTokenPtr view_token) {
+  DCHECK(owner_);
+  owner_.reset();
+  registry_->OnViewResolved(this, view_token.Pass());
+}
+
+}  // namespace view_manager