title: Need to get HTML source as string CEFPython
body: <p>I am trying to get HTML source as string from web URL using CEFPython
  I want <code>MainFrame</code>'s source content to be crawled and get string in </p>
  
  <pre class="lang-python prettyprint-override"><code>def save_screenshot(browser):    
      # Browser object provides GetUserData/SetUserData methods
      # for storing custom data associated with browser. The
      # "OnPaint.buffer_string" data is set in RenderHandler.OnPaint.
      buffer_string = browser.GetUserData("OnPaint.buffer_string")
      if not buffer_string:
          raise Exception("buffer_string is empty, OnPaint never called?")
      mainFrame = browser.GetMainFrame()
      print("Main frame is ", mainFrame)
      # print("buffer string" ,buffer_string)
  
      # visitor object
      visitorObj = cef_string()
      temp = mainFrame.GetSource(visitorObj).GetString()
      print("temp : ", temp)
  
      visitorText = mainFrame.GetText(temp)
      siteHTML = mainFrame.GetSource(visitorText)
      print("siteHTML is ", siteHTML)
  </code></pre>
  
  <p><strong>Problem:</strong>
  The code is returning nothing for siteHTML </p>