Fix devserver's handling of static images.

src/platform/dev/update_test.py

 #!/usr/bin/python
 
 import urllib2
 import sys
 import threading
 from urlparse import urljoin
 from xml.dom import minidom
 
 UPDATE_BLOB="""\
 <?xml version="1.0" encoding="UTF-8"?>
@@ skipping 62 matching lines @@
   print data
   root = update_dom.firstChild
   update_info = root.getElementsByTagName('updatecheck')[0]
   update_url = update_info.getAttribute('codebase')
   hash = update_info.getAttribute('hash')
   head_request = urllib2.Request(update_url)
   head_request.get_method = lambda: 'HEAD'
   try:
     fd = urllib2.urlopen(head_request)
   except urllib2.HTTPError, e:
+    # HTTP error
     print 'FAILED: unable to retrieve %s\n\t%s' % (update_url, e)
-    return False
-  length = int(fd.headers.getheaders('Content-Length')[0])
-  assert length > 0
-  print 'Got a valid update response.'
-  fd.close()
-  assert (urllib2.urlopen(urljoin(update_url, 'cksum')).read() == hash)
-  print 'Update cksum matched the one in the update XML.'
-  return _verify_download(update_url, length)
+    length = 0
+  else:
+    # HTTP succeeded
+    length = int(fd.headers.getheaders('Content-Length')[0])
+  finally:
+    fd.close()
+    return (length > 0)
 
 def test(num_clients):
   # Fake some concurrent requests for each autoupdate operation.
   for clients in range(num_clients):
     for op in (do_version_ping, do_badversion_ping):
       t = threading.Thread(target=op)
       t.start()
 
 if __name__ == '__main__':
   if len(sys.argv) > 1:
     num_clients = int(sys.argv[1])
   else:
     num_clients = 1
   test(num_clients)