Add setting to enable/disable WebGL.

See #612.

CHANGELOG.asciidoc

@@ -24,6 +24,7 @@ Added
 - There are now some example userscripts in `misc/userscripts`.
 - New command `:scroll-px` which replaces `:scroll` for pixel-exact scrolling.
 - New setting `ui -> smooth-scrolling`.
+- New setting `content -> webgl` to enable/disable https://www.khronos.org/webgl/[WebGL].
 
 Changed
 ~~~~~~~

doc/help/settings.asciidoc

@@ -135,6 +135,7 @@
 |<<content-allow-images,allow-images>>|Whether images are automatically loaded in web pages.
 |<<content-allow-javascript,allow-javascript>>|Enables or disables the running of JavaScript programs.
 |<<content-allow-plugins,allow-plugins>>|Enables or disables plugins in Web pages.
+|<<content-webgl,webgl>>|Enables or disables WebGL.
 |<<content-geolocation,geolocation>>|Allow websites to request geolocations.
 |<<content-notifications,notifications>>|Allow websites to show notifications.
 |<<content-javascript-can-open-windows,javascript-can-open-windows>>|Whether JavaScript programs can open new windows.
@@ -1150,6 +1151,17 @@ Valid values:
 
 Default: +pass:[false]+
 
+[[content-webgl]]
+=== webgl
+Enables or disables WebGL.
+
+Valid values:
+
+ * +true+
+ * +false+
+
+Default: +pass:[true]+
+
 [[content-geolocation]]
 === geolocation
 Allow websites to request geolocations.

qutebrowser/config/configdata.py

@@ -609,6 +609,10 @@ def data(readonly=False):
              'Qt plugins with a mimetype such as "application/x-qt-plugin" '
              "are not affected by this setting."),
 
+            ('webgl',
+             SettingValue(typ.Bool(), 'true'),
+             "Enables or disables WebGL."),
+
             ('geolocation',
              SettingValue(typ.BoolAsk(), 'ask'),
              "Allow websites to request geolocations."),

qutebrowser/config/websettings.py

@@ -254,6 +254,8 @@ MAPPINGS = {
         #   Attribute(QWebSettings.JavaEnabled),
         'allow-plugins':
             Attribute(QWebSettings.PluginsEnabled),
+        'webgl':
+            Attribute(QWebSettings.WebGLEnabled),
         'local-content-can-access-remote-urls':
             Attribute(QWebSettings.LocalContentCanAccessRemoteUrls),
         'local-content-can-access-file-urls':