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_global_extended_attr.py

@@ -0,0 +1,129 @@
+def WebIDLTest(parser, harness):
+    parser.parse(
+        """
+      [Global, Exposed=Foo]
+      interface Foo : Bar {
+        getter any(DOMString name);
+      };
+      [Exposed=Foo]
+      interface Bar {};
+    """
+    )
+
+    results = parser.finish()
+
+    harness.ok(
+        results[0].isOnGlobalProtoChain(),
+        "[Global] interface should be on global's proto chain",
+    )
+    harness.ok(
+        results[1].isOnGlobalProtoChain(),
+        "[Global] interface should be on global's proto chain",
+    )
+
+    parser = parser.reset()
+    threw = False
+    try:
+        parser.parse(
+            """
+          [Global, Exposed=Foo]
+          interface Foo {
+            getter any(DOMString name);
+            setter undefined(DOMString name, any arg);
+          };
+        """
+        )
+        results = parser.finish()
+    except:
+        threw = True
+
+    harness.ok(
+        threw,
+        "Should have thrown for [Global] used on an interface with a " "named setter",
+    )
+
+    parser = parser.reset()
+    threw = False
+    try:
+        parser.parse(
+            """
+          [Global, Exposed=Foo]
+          interface Foo {
+            getter any(DOMString name);
+            deleter undefined(DOMString name);
+          };
+        """
+        )
+        results = parser.finish()
+    except:
+        threw = True
+
+    harness.ok(
+        threw,
+        "Should have thrown for [Global] used on an interface with a " "named deleter",
+    )
+
+    parser = parser.reset()
+    threw = False
+    try:
+        parser.parse(
+            """
+          [Global, LegacyOverrideBuiltIns, Exposed=Foo]
+          interface Foo {
+          };
+        """
+        )
+        results = parser.finish()
+    except:
+        threw = True
+
+    harness.ok(
+        threw,
+        "Should have thrown for [Global] used on an interface with a "
+        "[LegacyOverrideBuiltIns]",
+    )
+
+    parser = parser.reset()
+    threw = False
+    try:
+        parser.parse(
+            """
+          [Global, Exposed=Foo]
+          interface Foo : Bar {
+          };
+          [LegacyOverrideBuiltIns, Exposed=Foo]
+          interface Bar {
+          };
+        """
+        )
+        results = parser.finish()
+    except:
+        threw = True
+
+    harness.ok(
+        threw,
+        "Should have thrown for [Global] used on an interface with an "
+        "[LegacyOverrideBuiltIns] ancestor",
+    )
+
+    parser = parser.reset()
+    threw = False
+    try:
+        parser.parse(
+            """
+          [Global, Exposed=Foo]
+          interface Foo {
+          };
+          [Exposed=Foo]
+          interface Bar : Foo {
+          };
+        """
+        )
+        results = parser.finish()
+    except:
+        threw = True
+
+    harness.ok(
+        threw,
+        "Should have thrown for [Global] used on an interface with a " "descendant",
+    )