ash: Initialize some pointers to null in SystemTray constructor

ash/system/tray/system_tray.cc

 // Copyright (c) 2012 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 "ash/system/tray/system_tray.h"
 
 #include "ash/ash_switches.h"
 #include "ash/metrics/user_metrics_recorder.h"
 #include "ash/shelf/shelf_layout_manager.h"
 #include "ash/shell.h"
@@ skipping 112 matching lines @@
 
   DISALLOW_COPY_AND_ASSIGN(SystemBubbleWrapper);
 };
 
 
 // SystemTray
 
 SystemTray::SystemTray(StatusAreaWidget* status_area_widget)
     : TrayBackgroundView(status_area_widget),
       items_(),
+      detailed_item_(nullptr),
       default_bubble_height_(0),
       hide_notifications_(false),
       full_system_tray_menu_(false),
-      tray_accessibility_(NULL),
-      tray_date_(NULL) {
+      tray_accessibility_(nullptr),
+      tray_cast_(nullptr),
+      tray_date_(nullptr),
+      screen_capture_tray_item_(nullptr),
+      screen_share_tray_item_(nullptr) {

[stevenjb, 2016/03/30 00:47:57]

Bleh. These probably shouldn't exist, but something for another day. Thanks for
cleaning this up.

   SetContentsBackground();
 }
 
 SystemTray::~SystemTray() {
   // Destroy any child views that might have back pointers before ~View().
   system_bubble_.reset();
   notification_bubble_.reset();
   for (std::vector<SystemTrayItem*>::iterator it = items_.begin();
        it != items_.end();
        ++it) {
@@ skipping 587 matching lines @@
   system_bubble_.reset();
   // When closing a system bubble with the alternate shelf layout, we need to
   // turn off the active tinting of the shelf.
   if (full_system_tray_menu_) {
     SetDrawBackgroundAsActive(false);
     full_system_tray_menu_ = false;
   }
 }
 
 }  // namespace ash