[Chrome OS MD] Update the color of update button and improve its appearance

ash/common/system/update/tray_update.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/common/system/update/tray_update.h"
 
 #include "ash/common/material_design/material_design_controller.h"
 #include "ash/common/metrics/user_metrics_action.h"
 #include "ash/common/system/tray/fixed_sized_image_view.h"
 #include "ash/common/system/tray/system_tray.h"
@@ skipping 46 matching lines @@
 // Returns the color to use for the material design update icon when the update
 // severity is |severity|. If |for_menu| is true, the icon color for the system
 // menu is given, otherwise the icon color for the system tray is given.
 SkColor IconColorForUpdateSeverity(UpdateInfo::UpdateSeverity severity,
                                    bool for_menu) {
   const SkColor default_color = for_menu ? kMenuIconColor : kTrayIconColor;
   switch (severity) {
     case UpdateInfo::UPDATE_NONE:
       return default_color;
     case UpdateInfo::UPDATE_LOW:
-      return for_menu ? gfx::kGoogleGreen700 : gfx::kGoogleGreen300;
+      return for_menu ? gfx::kGoogleGreen700 : kTrayIconColor;
     case UpdateInfo::UPDATE_ELEVATED:
       return for_menu ? gfx::kGoogleYellow700 : gfx::kGoogleYellow300;
     case UpdateInfo::UPDATE_HIGH:
     case UpdateInfo::UPDATE_SEVERE:
     case UpdateInfo::UPDATE_CRITICAL:
       return for_menu ? gfx::kGoogleRed700 : gfx::kGoogleRed300;
     default:
       NOTREACHED();
       break;
   }
@@ skipping 68 matching lines @@
 
 void TrayUpdate::OnUpdateRecommended(const UpdateInfo& info) {
   if (MaterialDesignController::UseMaterialDesignSystemIcons())
     SetIconColor(IconColorForUpdateSeverity(info.severity, false));
   else
     SetImageFromResourceId(DecideResource(info.severity, false));
   tray_view()->SetVisible(true);
 }
 
 }  // namespace ash