Add support for content -> cookies-store with QtWebEngine

CHANGELOG.asciidoc

@@ -25,6 +25,7 @@ Added
 - link:https://github.com/annulen/webkit/wiki[QtWebKit Reloaded] (also called QtWebKit-NG) is now supported.
 - Printing support for QtWebEngine with Qt >= 5.8
 - Proxy support for QtWebEngine with Qt >= 5.8
+- Support for the `content -> cookies-store`  option with QtWebEngine
 
 Changed
 ~~~~~~~

doc/help/settings.asciidoc

@@ -172,7 +172,7 @@
 |<<content-local-content-can-access-remote-urls,local-content-can-access-remote-urls>>|Whether locally loaded documents are allowed to access remote urls.
 |<<content-local-content-can-access-file-urls,local-content-can-access-file-urls>>|Whether locally loaded documents are allowed to access other local urls.
 |<<content-cookies-accept,cookies-accept>>|Control which cookies to accept.
-|<<content-cookies-store,cookies-store>>|Whether to store cookies.
+|<<content-cookies-store,cookies-store>>|Whether to store cookies. Note this option needs a restart with QtWebEngine.
 |<<content-host-block-lists,host-block-lists>>|List of URLs of lists which contain hosts to block.
 |<<content-host-blocking-enabled,host-blocking-enabled>>|Whether host blocking is enabled.
 |<<content-host-blocking-whitelist,host-blocking-whitelist>>|List of domains that should always be loaded, despite being ad-blocked.
@@ -1594,7 +1594,7 @@ This setting is only available with the QtWebKit backend.
 
 [[content-cookies-store]]
 === cookies-store
-Whether to store cookies.
+Whether to store cookies. Note this option needs a restart with QtWebEngine.
 
 Valid values:
 
@@ -1603,8 +1603,6 @@ Valid values:
 
 Default: +pass:[true]+
 
-This setting is only available with the QtWebKit backend.
-
 [[content-host-block-lists]]
 === host-block-lists
 List of URLs of lists which contain hosts to block.

qutebrowser/browser/webengine/webenginesettings.py

@@ -32,7 +32,7 @@ from PyQt5.QtWebEngineWidgets import (QWebEngineSettings, QWebEngineProfile,
 # pylint: enable=no-name-in-module,import-error,useless-suppression
 
 from qutebrowser.browser import shared
-from qutebrowser.config import websettings
+from qutebrowser.config import config, websettings
 from qutebrowser.utils import objreg, utils, standarddir, javascript
 
 
@@ -65,6 +65,21 @@ class StaticSetter(websettings.StaticSetter):
     GLOBAL_SETTINGS = QWebEngineSettings.globalSettings
 
 
+class PersistentCookiePolicy(websettings.Base):
+
+    """The cookies -> store setting is different from other settings."""
+
+    def get(self, settings=None):
+        return config.get('content', 'cookies-store')
+
+    def _set(self, value, settings=None):
+        utils.unused(settings)
+        QWebEngineProfile.defaultProfile().setPersistentCookiesPolicy(
+            QWebEngineProfile.AllowPersistentCookies if value else
+            QWebEngineProfile.NoPersistentCookies
+        )
+
+
 def _init_stylesheet(profile):
     """Initialize custom stylesheets.
 
@@ -121,6 +136,9 @@ def init(args):
     profile = QWebEngineProfile.defaultProfile()
     _init_profile(profile)
     _init_stylesheet(profile)
+    # We need to do this here as a WORKAROUND for
+    # https://bugreports.qt.io/browse/QTBUG-58650
+    PersistentCookiePolicy().set(config.get('content', 'cookies-store'))
 
     websettings.init_mappings(MAPPINGS)
     objreg.get('config').changed.connect(update_settings)
@@ -169,6 +187,9 @@ MAPPINGS = {
             Attribute(QWebEngineSettings.LocalContentCanAccessRemoteUrls),
         'local-content-can-access-file-urls':
             Attribute(QWebEngineSettings.LocalContentCanAccessFileUrls),
+        # https://bugreports.qt.io/browse/QTBUG-58650
+        # 'cookies-store':
+        #     PersistentCookiePolicy(),
     },
     'input': {
         'spatial-navigation':

qutebrowser/config/configdata.py

@@ -891,9 +891,9 @@ def data(readonly=False):
              "Control which cookies to accept."),
 
             ('cookies-store',
-             SettingValue(typ.Bool(), 'true',
-                          backends=[usertypes.Backend.QtWebKit]),
-             "Whether to store cookies."),
+             SettingValue(typ.Bool(), 'true'),
+             "Whether to store cookies. Note this option needs a restart with "
+             "QtWebEngine."),
 
             ('host-block-lists',
              SettingValue(