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_replaceable.py

@@ -0,0 +1,84 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+
+def should_throw(parser, harness, message, code):
+    parser = parser.reset()
+    threw = False
+    try:
+        parser.parse(code)
+        parser.finish()
+    except:
+        threw = True
+
+    harness.ok(threw, "Should have thrown: %s" % message)
+
+
+def WebIDLTest(parser, harness):
+    # The [Replaceable] extended attribute MUST take no arguments.
+    should_throw(
+        parser,
+        harness,
+        "no arguments",
+        """
+        interface I {
+          [Replaceable=X] readonly attribute long A;
+        };
+    """,
+    )
+
+    # An attribute with the [Replaceable] extended attribute MUST NOT also be
+    # declared with the [PutForwards] extended attribute.
+    should_throw(
+        parser,
+        harness,
+        "PutForwards",
+        """
+        interface I {
+          [PutForwards=B, Replaceable] readonly attribute J A;
+        };
+        interface J {
+          attribute long B;
+        };
+    """,
+    )
+
+    # The [Replaceable] extended attribute MUST NOT be used on an attribute
+    # that is not read only.
+    should_throw(
+        parser,
+        harness,
+        "writable attribute",
+        """
+        interface I {
+          [Replaceable] attribute long A;
+        };
+    """,
+    )
+
+    # The [Replaceable] extended attribute MUST NOT be used on a static
+    # attribute.
+    should_throw(
+        parser,
+        harness,
+        "static attribute",
+        """
+        interface I {
+          [Replaceable] static readonly attribute long A;
+        };
+    """,
+    )
+
+    # The [Replaceable] extended attribute MUST NOT be used on an attribute
+    # declared on a callback interface.
+    should_throw(
+        parser,
+        harness,
+        "callback interface",
+        """
+        callback interface I {
+          [Replaceable] readonly attribute long A;
+        };
+    """,
+    )