mash: Add SystemTrayClient interface, use to show date settings

ash/mus/system_tray_delegate_mus.cc

Index: ash/mus/system_tray_delegate_mus.cc
diff --git a/ash/mus/system_tray_delegate_mus.cc b/ash/mus/system_tray_delegate_mus.cc
index 8add535aa2bf63f0e61f51d57121d91a21396604..f2afff5527e22ea33723c2f96543ae0273b0415b 100644
--- a/ash/mus/system_tray_delegate_mus.cc
+++ b/ash/mus/system_tray_delegate_mus.cc
@@ -6,8 +6,11 @@
 
 #include "ash/common/system/tray/system_tray_notifier.h"
 #include "ash/common/wm_shell.h"
+#include "base/bind.h"
+#include "base/bind_helpers.h"
 #include "base/i18n/time_formatting.h"
 #include "base/logging.h"
+#include "services/shell/public/cpp/connector.h"
 
 namespace ash {
 namespace {
@@ -16,8 +19,9 @@ SystemTrayDelegateMus* g_instance = nullptr;
 
 }  // namespace
 
-SystemTrayDelegateMus::SystemTrayDelegateMus()
-    : hour_clock_type_(base::GetHourClockType()) {
+SystemTrayDelegateMus::SystemTrayDelegateMus(shell::Connector* connector)
+    : connector_(connector), hour_clock_type_(base::GetHourClockType()) {
+  // Don't make an initial connection to exe:chrome. Do it on demand.
   DCHECK(!g_instance);
   g_instance = this;
 }
@@ -32,10 +36,30 @@ SystemTrayDelegateMus* SystemTrayDelegateMus::Get() {
   return g_instance;
 }
 
+void SystemTrayDelegateMus::ConnectToSystemTrayClient() {
+  if (system_tray_client_.is_bound())
+    return;
+
+  connector_->ConnectToInterface("exe:chrome", &system_tray_client_);
+
+  // Tolerate chrome crashing and coming back up.
+  system_tray_client_.set_connection_error_handler(base::Bind(
+      &SystemTrayDelegateMus::OnClientConnectionError, base::Unretained(this)));
+}
+
+void SystemTrayDelegateMus::OnClientConnectionError() {
+  system_tray_client_.reset();
+}
+
 base::HourClockType SystemTrayDelegateMus::GetHourClockType() const {
   return hour_clock_type_;
 }
 
+void SystemTrayDelegateMus::ShowDateSettings() {
+  ConnectToSystemTrayClient();
+  system_tray_client_->ShowDateSettings();
+}
+
 void SystemTrayDelegateMus::SetUse24HourClock(bool use_24_hour) {
   hour_clock_type_ = use_24_hour ? base::k24HourClock : base::k12HourClock;
   WmShell::Get()->system_tray_notifier()->NotifyDateFormatChanged();