Bug 1287723 - Fix test_screenshot.py to properly wait for new chrome window to be loaded. r=automatedtester

MozReview-Commit-ID: KiFGbNdddJe

--HG--
extra : rebase_source : 87ccbb02cdb45531efc7fe948c57c10e9e03b547

testing/marionette/harness/marionette/tests/unit/test_screenshot.py

@@ -6,7 +6,6 @@ import base64
 import hashlib
 import imghdr
 import struct
-import time
 import urllib
 
 from unittest import skip
@@ -87,16 +86,21 @@ class Chrome(ScreenCaptureTestCase):
     # <window> element, which does not exist for secondary windows.
     def test_secondary_windows(self):
         ss = self.marionette.screenshot()
-        self.marionette.execute_script("""
-            window.open('chrome://marionette/content/doesnotexist.xul',
+        self.marionette.execute_async_script("""
+            win = window.open('chrome://marionette/content/doesnotexist.xul',
             'foo',
             'chrome');
+
+            // Bug 1288339 - We don't wait for readyState to be complete yet
+            waitForWindow = function() {
+              if (win.document.readyState != 'complete') {
+                win.setTimeout(this, 100);
+              }
+
+              marionetteScriptFinished(true);
+            }()
             """)
         self.marionette.switch_to_window("foo")
-        # there can be a race between opening and registering the window
-        # and switching to it. Waiting a tiny amount of time is enough not to
-        # break anything.
-        time.sleep(0.002)
         ss = self.marionette.screenshot()
         size = self.get_image_dimensions(ss)
         self.assert_png(ss)