mash: Add SystemTrayClient interface, use to show date settings

chrome/browser/ui/ash/system_tray_client.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 "chrome/browser/ui/ash/system_tray_controller_mus.h"
+#include "chrome/browser/ui/ash/system_tray_client.h"
 
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/browser_process_platform_part.h"
 #include "chrome/browser/chromeos/system/system_clock.h"
+#include "chrome/browser/ui/ash/system_tray_common.h"
 #include "content/public/common/mojo_shell_connection.h"
 #include "services/shell/public/cpp/connector.h"
 
-SystemTrayControllerMus::SystemTrayControllerMus() {
-  shell::Connector* connector =
-      content::MojoShellConnection::GetForProcess()->GetConnector();
-  connector->ConnectToInterface("mojo:ash", &system_tray_);
+namespace {
 
+SystemTrayClient* g_instance = nullptr;
+
+}  // namespace
+
+SystemTrayClient::SystemTrayClient() : binding_(this) {
+  // Connect to the mojo SystemTray service in ash.
+  ConnectToSystemTray();
+
+  // If this observes clock setting changes before ash comes up the IPCs will
+  // be queued on |system_tray_|.
   g_browser_process->platform_part()->GetSystemClock()->AddObserver(this);
+
+  DCHECK(!g_instance);
+  g_instance = this;
 }
 
-SystemTrayControllerMus::~SystemTrayControllerMus() {
+SystemTrayClient::~SystemTrayClient() {
+  DCHECK_EQ(this, g_instance);
+  g_instance = nullptr;
+
   g_browser_process->platform_part()->GetSystemClock()->RemoveObserver(this);
 }
 
-void SystemTrayControllerMus::OnSystemClockChanged(
+// static
+SystemTrayClient* SystemTrayClient::Get() {
+  return g_instance;
+}
+
+void SystemTrayClient::ConnectToSystemTray() {
+  // Check if already connected.
+  if (system_tray_.is_bound())
+    return;
+
+  // Connect to ash.
+  content::MojoShellConnection::GetForProcess()
+      ->GetConnector()
+      ->ConnectToInterface("mojo:ash", &system_tray_);
+
+  // Tolerate ash crashing and coming back up. This object is destroyed after
+  // main message loop shutdown so Bind() doesn't need a weak pointer.
+  system_tray_.set_connection_error_handler(base::Bind(
+      &SystemTrayClient::OnClientConnectionError, base::Unretained(this)));
+}
+
+void SystemTrayClient::OnClientConnectionError() {
+  system_tray_.reset();
+}
+
+void SystemTrayClient::ShowDateSettings() {
+  SystemTrayCommon::ShowDateSettings();
+}
+
+void SystemTrayClient::OnSystemClockChanged(
     chromeos::system::SystemClock* clock) {
+  ConnectToSystemTray();
   system_tray_->SetUse24HourClock(clock->ShouldUse24HourClock());
 }