Create a top-level "third_party" directory

This directory now contains third_party software that is vendored into
the Servo source tree. The idea is that it would eventually hold
webrender and other crates from mozilla-central as well with a standard
patch management approach for each.

third_party/WebIDL/tests/test_conditional_dictionary_member.py

@@ -0,0 +1,128 @@
+def WebIDLTest(parser, harness):
+    parser.parse(
+        """
+      dictionary Dict {
+        any foo;
+        [ChromeOnly] any bar;
+      };
+    """
+    )
+    results = parser.finish()
+    harness.check(len(results), 1, "Should have a dictionary")
+    members = results[0].members
+    harness.check(len(members), 2, "Should have two members")
+    # Note that members are ordered lexicographically, so "bar" comes
+    # before "foo".
+    harness.ok(
+        members[0].getExtendedAttribute("ChromeOnly"), "First member is not ChromeOnly"
+    )
+    harness.ok(
+        not members[1].getExtendedAttribute("ChromeOnly"), "Second member is ChromeOnly"
+    )
+
+    parser = parser.reset()
+    parser.parse(
+        """
+      dictionary Dict {
+        any foo;
+        any bar;
+      };
+
+      interface Iface {
+        [Constant, Cached] readonly attribute Dict dict;
+      };
+    """
+    )
+    results = parser.finish()
+    harness.check(len(results), 2, "Should have a dictionary and an interface")
+
+    parser = parser.reset()
+    exception = None
+    try:
+        parser.parse(
+            """
+        dictionary Dict {
+          any foo;
+          [ChromeOnly] any bar;
+        };
+
+        interface Iface {
+          [Constant, Cached] readonly attribute Dict dict;
+        };
+      """
+        )
+        results = parser.finish()
+    except Exception as e:
+        exception = e
+
+    harness.ok(exception, "Should have thrown.")
+    harness.check(
+        exception.message,
+        "[Cached] and [StoreInSlot] must not be used on an attribute "
+        "whose type contains a [ChromeOnly] dictionary member",
+        "Should have thrown the right exception",
+    )
+
+    parser = parser.reset()
+    exception = None
+    try:
+        parser.parse(
+            """
+        dictionary ParentDict {
+          [ChromeOnly] any bar;
+        };
+
+        dictionary Dict : ParentDict {
+          any foo;
+        };
+
+        interface Iface {
+          [Constant, Cached] readonly attribute Dict dict;
+        };
+      """
+        )
+        results = parser.finish()
+    except Exception as e:
+        exception = e
+
+    harness.ok(exception, "Should have thrown (2).")
+    harness.check(
+        exception.message,
+        "[Cached] and [StoreInSlot] must not be used on an attribute "
+        "whose type contains a [ChromeOnly] dictionary member",
+        "Should have thrown the right exception (2)",
+    )
+
+    parser = parser.reset()
+    exception = None
+    try:
+        parser.parse(
+            """
+        dictionary GrandParentDict {
+          [ChromeOnly] any baz;
+        };
+
+        dictionary ParentDict : GrandParentDict {
+          any bar;
+        };
+
+        dictionary Dict : ParentDict {
+          any foo;
+        };
+
+        interface Iface {
+          [Constant, Cached] readonly attribute Dict dict;
+        };
+      """
+        )
+        results = parser.finish()
+    except Exception as e:
+        exception = e
+
+    harness.ok(exception, "Should have thrown (3).")
+    harness.check(
+        exception.message,
+        "[Cached] and [StoreInSlot] must not be used on an attribute "
+        "whose type contains a [ChromeOnly] dictionary member",
+        "Should have thrown the right exception (3)",
+    )