[SystemInfo API] Move Storage API out of experimental namespace and rename to the "system" namespace

tools/metrics/histograms/histograms.xml

 <!--
 Copyright 2013 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.
 -->
 
 <!--
 This file is used to generate a comprehensive list of Chrome histograms along
 with a detailed description for each histogram.
 
@@ skipping 15422 matching lines @@
   <int value="496" label="FILEBROWSERPRIVATE_ZOOM"/>
   <int value="497" label="WEBVIEW_GO"/>
   <int value="498" label="WEBSTOREPRIVATE_ISININCOGNITOMODEFUNCTION"/>
   <int value="499" label="FILEBROWSERPRIVATE_REQUESTACCESSTOKEN"/>
   <int value="500" label="WEBVIEW_STOP"/>
   <int value="501" label="WEBVIEW_RELOAD"/>
   <int value="502" label="WEBVIEW_TERMINATE"/>
   <int value="503" label="TYPES_PRIVATE_CHROMEDIRECTSETTING_GET"/>
   <int value="504" label="TYPES_PRIVATE_CHROMEDIRECTSETTING_SET"/>
   <int value="505" label="TYPES_PRIVATE_CHROMEDIRECTSETTING_CLEAR"/>
+  <int value="506" label="SYSTEMINFO_STORAGE_GET"/>
+  <int value="507" label="SYSTEMINFO_STORAGE_EJECTDEVICE"/>
 </enum>
 
 <enum name="ExtensionInstallCause" type="int">
   <int value="0" label="INSTALL_CAUSE_UNSET"/>
   <int value="1" label="INSTALL_CAUSE_USER_DOWNLOAD"/>
   <int value="2" label="INSTALL_CAUSE_UPDATE"/>
   <int value="3" label="INSTALL_CAUSE_EXTERNAL_FILE"/>
   <int value="4" label="INSTALL_CAUSE_AUTOMATION"/>
 </enum>
 
@@ skipping 6292 matching lines @@
   <group name="Disabled" label="Neither extra webstore link is visible"/>
   <group name="FooterLink" label="Link in bottom right of footer"/>
   <group name="PlusIcon" label="Plus icon in apps page"/>
   <affected-histogram name="Extensions.AppLaunch"/>
   <affected-histogram name="NewTabPage.DefaultPageType"/>
 </fieldtrial>
 
 </fieldtrials>
 
 </histogram-configuration>