Greasemonkey: add minimal end-to-end test.

Just runs a greasemonkey script on a test page and uses console.log to
ensure it is running.

Tests @include, and basic happy path greasemonkey.py operation (loading
and parsing script, scrip_for on webkit), only testing document-start
injecting point but that is the troublsome one at this point.

Tested on py35 debian unstable (oldwebkit and qtwebengine5.9) debian
stable qtwebengine5.7.

Note the extra :reload call for qt5.7 because document-start scripts
don't seem to run on the first page load with the current insertion
point. I need to look into this more to look at ways of fixing this.

tests/end2end/features/javascript.feature

@@ -123,3 +123,12 @@ Feature: Javascript stuff
         And I wait for "[*/data/javascript/windowsize.html:*] loaded" in the log
         And I run :tab-next
         Then the window sizes should be the same
+
+    Scenario: Have a greasemonkey script run on a page
+        When I have a greasemonkey file saved
+        And I run :greasemonkey-reload
+        And I open data/title.html
+        # This second reload is required in webengine < 5.8 for scripts
+        # registered to run at document-start, some sort of timing issue.
+        And I run :reload
+        Then the javascript message "Script is running." should be logged

tests/end2end/features/test_javascript_bdd.py

@@ -17,6 +17,8 @@
 # You should have received a copy of the GNU General Public License
 # along with qutebrowser.  If not, see <http://www.gnu.org/licenses/>.
 
+import os.path
+
 import pytest_bdd as bdd
 bdd.scenarios('javascript.feature')
 
@@ -29,3 +31,23 @@ def check_window_sizes(quteproc):
     hidden_size = hidden.message.split()[-1]
     visible_size = visible.message.split()[-1]
     assert hidden_size == visible_size
+
+test_gm_script="""
+// ==UserScript==
+// @name Qutebrowser test userscript
+// @namespace invalid.org
+// @include http://localhost:*/data/title.html
+// @exclude ???
+// @run-at document-start
+// ==/UserScript==
+console.log("Script is running on " + window.location.pathname);
+"""
+
+@bdd.when("I have a greasemonkey file saved")
+def create_greasemonkey_file(quteproc):
+    script_path = os.path.join(quteproc.basedir, 'data', 'greasemonkey')
+    os.mkdir(script_path)
+    file_path = os.path.join(script_path, 'test.user.js')
+    with open(file_path, 'w', encoding='utf-8') as f:
+        f.write(test_gm_script)
+