dom-ui settings: Fix enabled state of commit button in Clear Browsing Data dialog.

BUG=70715
TEST=Verify commit button is enabled when at least one data type is selected.
Review URL: http://codereview.chromium.org/6368014

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@72509 0039d316-1c4b-4281-b951-d872f2087c98

chrome/browser/resources/options/clear_browser_data_overlay.html

 <div id="clearBrowserDataOverlay" class="page hidden">
   <h1 i18n-content="clearBrowserDataTitle"></h1>
-  <div class="content-area">
+  <div id="cbdContentArea" class="content-area">
     <span i18n-content="clearBrowserDataLabel"></span>
     <select id="clearBrowserDataTimePeriod"
         i18n-options="clearBrowserDataTimeList"