title: Watir - file_field.exists? comes up as false even though there is an upload form on the page
body: <p>I am looking at a web page with an overlay that contains a Choose File/Browse etc button
  Below is a snippet from the page</p>
  
  <pre><code>&lt;form name = "form1" method = "post" action = "UploadPhoto.aspx?PhotoUploaderFor=1" id = "form1" enctype = "multipart/form-data"&gt;
  &lt;div&gt;...&lt;/div&gt;
  &lt;div class = "popup-form photoUploader"&gt;
   &lt;div class = "group data-row"&gt;
    &lt;label&gt;...&lt;/label&gt;
    &lt;input type ="file" name = "FileUpload1" id = "FileUpload1" class = "browse_file"&gt;
  </code></pre>
  
  <p>Watir has file_fields which can handle file uploads
  I've tried on the test site (www.tinypic.com) and the controls work fine there</p>
  
  <pre><code>b.file_fields.exists? 
  </code></pre>
  
  <p>will return true</p>
  
  <p>However, on the page i'm looking at with the snippet above, </p>
  
  <pre><code> b.file_fields.exists? 
  </code></pre>
  
  <p>returns false</p>
  
  <p>I thought it might be because of the form, so I also tried </p>
  
  <pre><code>b.form(:name =&gt; "form1").file_fields.exists?
  </code></pre>
  
  <p>Which also returns false
  If i try to access the button itself directly, this also returns false</p>
  
  <pre><code>b.element(:xpath =&gt; "//input [@name = 'FileUpload1']").exists?
  </code></pre>
  
  <p>Anyone have any ideas?</p>
  
  <p>EDIT</p>
  
  <p>The form is inside an iframe</p>
  
  <pre><code>&lt;iframe id="Step1_Banner1_Popup_Photo_Photo_Iframe_PhotoUploader" class="photoUploaderFrame" scrolling="no" src="../MSReport3/UserControls/UploadPhoto.aspx?PhotoUploaderFor=1"&gt;
  #document
   &lt;!DOCTYPE html PUBLIC "-//W3C//DTD CHTML 1.0 ....."&gt;
    &lt;html xmlns = "http://www.w3.org/1999/xhtml"&gt;
     &lt;head&gt;...&lt;/head&gt;
     &lt;body&gt;
     &lt;code from above goes here&gt;
  </code></pre>