Typecheck some of ui/webui/resources/js/ with Closure compiler.

ui/webui/resources/js/assert.js

Index: ui/webui/resources/js/assert.js
diff --git a/ui/webui/resources/js/assert.js b/ui/webui/resources/js/assert.js
index bae2910705bd3eb77270c46cf7ec1fb6dbac82a0..1e25769387975e7c8da75c51b132a9459dcb0914 100644
--- a/ui/webui/resources/js/assert.js
+++ b/ui/webui/resources/js/assert.js
@@ -22,3 +22,11 @@ function assert(condition, opt_message) {
     throw new Error(msg);
   }
 }
+
+/**
+ * Insert a notReached() in cases where control flow should never hit.
+ * @param {string=} opt_message A message to show when this is hit.
+ */
+function notReached(opt_message) {

[arv (Not doing code reviews), 2014/07/24 16:44:24]

How about assertNotReached instead?

[Dan Beam, 2014/07/25 01:52:32]

hmmm, blink uses ASSERT_NOT_REACHED() while chrome uses NOTREACHED.

"assertNotReached" is clearer than "notReached" (arguably), but
"assertNotReached" is longer than "assert(false, " or "notReached".

whatever, "assertNotReached" it is.

+  throw new Error(opt_message || "Unreachable code hit");
+}