Prioritize ARC instance only when it is needed

chrome/browser/chromeos/arc/boot_phase_monitor/arc_instance_throttle.cc

+// Copyright 2017 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/arc/boot_phase_monitor/arc_instance_throttle.h"
+
+#include "ash/common/wm_shell.h"
+#include "ash/common/wm_window.h"
+#include "ash/shared/app_types.h"
+#include "base/bind.h"
+#include "base/logging.h"
+#include "chromeos/dbus/dbus_thread_manager.h"
+#include "chromeos/dbus/session_manager_client.h"
+
+namespace arc {
+
+namespace {
+
+void OnDBusReply(bool is_prioritize, bool success) {
+  if (success)
+    return;
+  const char* message = is_prioritize ? "unprioritize" : "prioritize";
+  LOG(WARNING) << "Failed to " << message << " the instance";
+}
+
+bool IsArcAppWindow(ash::WmWindow* active) {
+  return active->GetAppType() == static_cast<int>(ash::AppType::ARC_APP);
+}
+
+void ThrottleInstanceIfNeeded(ash::WmWindow* active) {
+  chromeos::SessionManagerClient* session_manager_client =
+      chromeos::DBusThreadManager::Get()->GetSessionManagerClient();
+  if (!session_manager_client) {
+    LOG(WARNING) << "SessionManagerClient is not available";
+    return;
+  }
+  if (!active || !IsArcAppWindow(active)) {
+    // TODO(yusukes): Call session_manager_client->UnprioritizeArcInstance()

[Yusuke Sato, 2017/01/10 22:19:27]

It's under review at https://chromium-review.googlesource.com/#/c/425450/. Once
this is submitted, I'll pull the dbus constant to Chrome and add the method to
Chrome's SessionManagerClient.

+    // once it's ready.
+  } else {
+    session_manager_client->PrioritizeArcInstance(
+        base::Bind(OnDBusReply, true));
+  }
+}
+
+}  // namespace
+
+ArcInstanceThrottle::ArcInstanceThrottle() {
+  ash::WmShell* shell = ash::WmShell::Get();
+  DCHECK(shell);
+  shell->AddActivationObserver(this);
+  ThrottleInstanceIfNeeded(shell->GetActiveWindow());
+}
+
+ArcInstanceThrottle::~ArcInstanceThrottle() {
+  ash::WmShell* shell = ash::WmShell::Get();
+  if (shell)
+    shell->RemoveActivationObserver(this);
+}
+
+void ArcInstanceThrottle::OnWindowActivated(ash::WmWindow* gained_active,
+                                            ash::WmWindow* lost_active) {
+  ThrottleInstanceIfNeeded(gained_active);
+}
+
+}  // namespace arc