Add a script to list all CSS properties parsed by Servo.

components/style/list_properties.py

@@ -0,0 +1,14 @@
+#!/bin/env python2.7
+
+import os.path
+import sys
+
+style = os.path.dirname(__file__)
+sys.path.insert(0, os.path.join(style, "Mako-0.9.1.zip"))
+
+from mako.template import Template
+template = Template(filename=os.path.join(style, "properties.mako.rs"), input_encoding='utf8')
+template.render()
+properties = template.module.LONGHANDS + template.module.SHORTHANDS
+for name in sorted(p.name for p in properties):
+    print(name)

python/servo/testing_commands.py

@@ -158,6 +158,14 @@ class MachCommands(CommandBase):
     @CommandArgument('test_name', nargs=argparse.REMAINDER,
                      help="Only run tests that match this pattern or file path")
     def test_unit(self, test_name=None, package=None):
+        properties = subprocess.check_output([
+            sys.executable,
+            path.join(self.context.topdir, "components", "style", "list_properties.py")
+        ]).splitlines()
+        assert len(properties) >= 100
+        assert "margin-top" in properties
+        assert "margin" in properties
+
         if test_name is None:
             test_name = []