Bug 19402: download_pdf - resize Window to make sure it is large enough

On our Windows test server, the resolution is low, and the Download
button is not displayed when the window is not large enough. Resizing it
fix the problem.

marionette/tor_browser_tests/test_download_pdf.py

@@ -21,6 +21,7 @@ class Test(MarionetteTestCase):
         m = self.marionette
 
         m.set_search_timeout(1000)
+        m.set_window_size(1024, 300)
 
         with m.using_context('content'):