Explicitly mark first 2 args of addEventListener/removeEventListener as optional

LayoutTests/fast/dom/event-target-arguments-expected.txt

Index: LayoutTests/fast/dom/event-target-arguments-expected.txt
diff --git a/LayoutTests/fast/dom/event-target-arguments-expected.txt b/LayoutTests/fast/dom/event-target-arguments-expected.txt
index eec10fd6b6da7c990bb5156fbb534b2535e477ae..46d86e5dfb07ad148a8ab18d1177f0550b19871b 100644
--- a/LayoutTests/fast/dom/event-target-arguments-expected.txt
+++ b/LayoutTests/fast/dom/event-target-arguments-expected.txt
@@ -12,8 +12,13 @@ PASS document.addEventListener("", listener) did not throw exception.
 PASS document.addEventListener("", function(){}) did not throw exception.
 PASS document.addEventListener("bar", listener, false) did not throw exception.
 PASS document.addEventListener("bar", listener, true) did not throw exception.
+PASS document.addEventListener(null) is undefined
 PASS document.addEventListener(null, listener) did not throw exception.
+PASS document.addEventListener("foo", null) is undefined
 PASS document.addEventListener("zork", listener, null) did not throw exception.
+PASS document.addEventListener(undefined) is undefined
+PASS document.addEventListener(undefined, listener) is undefined
+PASS document.addEventListener("foo", undefined) is undefined
 PASS document.addEventListener("zork", listener, undefined) did not throw exception.
 
 Signature:
@@ -24,9 +29,14 @@ PASS document.removeEventListener("foo", listener) did not throw exception.
 PASS document.removeEventListener("foo", listener, true) did not throw exception.
 PASS document.removeEventListener("bar", listener, false) did not throw exception.
 PASS document.removeEventListener("bar", listener, false) did not throw exception.
-PASS document.addEventListener("bar", listener, true) did not throw exception.
+PASS document.removeEventListener("bar", listener, true) did not throw exception.
+PASS document.removeEventListener(null) is undefined
 PASS document.removeEventListener(null, listener) did not throw exception.
+PASS document.removeEventListener("foo", null) is undefined
 PASS document.removeEventListener("zork", listener, null) did not throw exception.
+PASS document.removeEventListener(undefined) is undefined
+PASS document.removeEventListener(undefined, listener) is undefined
+PASS document.removeEventListener("foo", undefined) is undefined
 PASS document.removeEventListener("zork", listener, undefined) did not throw exception.
 PASS successfullyParsed is true