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_putForwards.py

@@ -0,0 +1,119 @@
+def WebIDLTest(parser, harness):
+    threw = False
+    try:
+        parser.parse(
+            """
+            interface I {
+              [PutForwards=B] readonly attribute long A;
+            };
+        """
+        )
+
+        results = parser.finish()
+    except:
+        threw = True
+
+    harness.ok(threw, "Should have thrown.")
+
+    parser = parser.reset()
+    threw = False
+    try:
+        parser.parse(
+            """
+            interface I {
+              [PutForwards=B] readonly attribute J A;
+            };
+            interface J {
+            };
+        """
+        )
+
+        results = parser.finish()
+    except:
+        threw = True
+
+    harness.ok(threw, "Should have thrown.")
+
+    parser = parser.reset()
+    threw = False
+    try:
+        parser.parse(
+            """
+            interface I {
+              [PutForwards=B] attribute J A;
+            };
+            interface J {
+              attribute long B;
+            };
+        """
+        )
+
+        results = parser.finish()
+    except:
+        threw = True
+
+    harness.ok(threw, "Should have thrown.")
+
+    parser = parser.reset()
+    threw = False
+    try:
+        parser.parse(
+            """
+            interface I {
+              [PutForwards=B] static readonly attribute J A;
+            };
+            interface J {
+              attribute long B;
+            };
+        """
+        )
+
+        results = parser.finish()
+    except:
+        threw = True
+
+    harness.ok(threw, "Should have thrown.")
+
+    parser = parser.reset()
+    threw = False
+    try:
+        parser.parse(
+            """
+            callback interface I {
+              [PutForwards=B] readonly attribute J A;
+            };
+            interface J {
+              attribute long B;
+            };
+        """
+        )
+
+        results = parser.finish()
+    except:
+        threw = True
+
+    harness.ok(threw, "Should have thrown.")
+
+    parser = parser.reset()
+    threw = False
+    try:
+        parser.parse(
+            """
+            interface I {
+              [PutForwards=C] readonly attribute J A;
+              [PutForwards=C] readonly attribute J B;
+            };
+            interface J {
+              [PutForwards=D] readonly attribute K C;
+            };
+            interface K {
+              [PutForwards=A] readonly attribute I D;
+            };
+        """
+        )
+
+        results = parser.finish()
+    except:
+        threw = True
+
+    harness.ok(threw, "Should have thrown.")