Reimplement (address -> code) mapping from tickprocessor.py in JS.

test/mjsunit/mjsunit.js

Index: test/mjsunit/mjsunit.js
diff --git a/test/mjsunit/mjsunit.js b/test/mjsunit/mjsunit.js
index 3570d689ce550443072fca93a2bdbc68f6043ef6..370d491f8f9c66f6e39747b690673bd8511716ac 100644
--- a/test/mjsunit/mjsunit.js
+++ b/test/mjsunit/mjsunit.js
@@ -113,6 +113,20 @@ function assertNaN(value, name_opt) {
 }
 
 
+function assertNull(value, name_opt) {
+  if (value !== null) {
+    fail("null", value, name_opt);
+  }
+}
+
+
+function assertNotNull(value, name_opt) {
+  if (value === null) {
+    fail("not null", value, name_opt);
+  }
+}
+
+
 function assertThrows(code) {
   var threwException = true;
   try {