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_cereactions.py

@@ -0,0 +1,157 @@
+def WebIDLTest(parser, harness):
+    threw = False
+    try:
+        parser.parse(
+            """
+            interface Foo {
+              [CEReactions(DOMString a)] undefined foo(boolean arg2);
+            };
+        """
+        )
+
+        results = parser.finish()
+    except:
+        threw = True
+
+    harness.ok(threw, "Should have thrown for [CEReactions] with an argument")
+
+    parser = parser.reset()
+    threw = False
+    try:
+        parser.parse(
+            """
+            interface Foo {
+              [CEReactions(DOMString b)] readonly attribute boolean bar;
+            };
+        """
+        )
+
+        results = parser.finish()
+    except:
+        threw = True
+
+    harness.ok(threw, "Should have thrown for [CEReactions] with an argument")
+
+    parser = parser.reset()
+    threw = False
+    try:
+        parser.parse(
+            """
+            interface Foo {
+              [CEReactions] attribute boolean bar;
+            };
+        """
+        )
+
+        results = parser.finish()
+    except Exception as e:
+        harness.ok(
+            False,
+            "Shouldn't have thrown for [CEReactions] used on writable attribute. %s"
+            % e,
+        )
+        threw = True
+
+    parser = parser.reset()
+    threw = False
+    try:
+        parser.parse(
+            """
+            interface Foo {
+              [CEReactions] undefined foo(boolean arg2);
+            };
+        """
+        )
+
+        results = parser.finish()
+    except Exception as e:
+        harness.ok(
+            False,
+            "Shouldn't have thrown for [CEReactions] used on regular operations. %s"
+            % e,
+        )
+        threw = True
+
+    parser = parser.reset()
+    threw = False
+    try:
+        parser.parse(
+            """
+            interface Foo {
+              [CEReactions] readonly attribute boolean A;
+            };
+        """
+        )
+
+        results = parser.finish()
+    except:
+        threw = True
+
+    harness.ok(
+        threw, "Should have thrown for [CEReactions] used on a readonly attribute"
+    )
+
+    parser = parser.reset()
+    threw = False
+    try:
+        parser.parse(
+            """
+            [CEReactions]
+            interface Foo {
+            }
+        """
+        )
+
+        results = parser.finish()
+    except:
+        threw = True
+
+    harness.ok(threw, "Should have thrown for [CEReactions] used on a interface")
+
+    parser = parser.reset()
+    threw = False
+    try:
+        parser.parse(
+            """
+          interface Foo {
+            [CEReactions] getter any(DOMString name);
+          };
+        """
+        )
+        results = parser.finish()
+    except:
+        threw = True
+
+    harness.ok(threw, "Should have thrown for [CEReactions] used on a named getter")
+
+    parser = parser.reset()
+    threw = False
+    try:
+        parser.parse(
+            """
+          interface Foo {
+            [CEReactions] legacycaller double compute(double x);
+          };
+        """
+        )
+        results = parser.finish()
+    except:
+        threw = True
+
+    harness.ok(threw, "Should have thrown for [CEReactions] used on a legacycaller")
+
+    parser = parser.reset()
+    threw = False
+    try:
+        parser.parse(
+            """
+          interface Foo {
+            [CEReactions] stringifier DOMString ();
+          };
+        """
+        )
+        results = parser.finish()
+    except:
+        threw = True
+
+    harness.ok(threw, "Should have thrown for [CEReactions] used on a stringifier")