title: 100% width for a field in a toolbar
body: <p>I am putting a search field in a gridpanel toolbar like this:</p>
  
  <pre><code>var searchGrid = Ext.create('Ext.grid.Panel', {
      store: searchStore,
      columns: [searchColumns],
      hideHeaders: true,
      tbar: [{
          xtype: 'searchfield',
          store: searchStore
      }],
      listeners: {
          itemclick: function(v,record) {
              // do stuff
          }
      }
  });
  </code></pre>
  
  <p><img src="https://i.stack.imgur.com/2iZQh.png" alt="enter image description here"></p>
  
  <p>I would like my search field to extend the full width of the grid. I know that I can add a listener to the grid that will resize the search field whenever the grid size changes, but does anyone know of a config or something cleaner that I missed?</p>