Update chai.js 3.4.1 --> 3.5.0.

This allows us to take advantage of the corresponding contributed externs
file rather than roll our own.

This is not the latest release of chai.js (4.2.0 is), but it's the one
that has an available externs file.

Bug: 1000989
Change-Id: I7045efdcfbc12025b6857178c11fc5195d8dbaed
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1888619
Commit-Queue: Trent Apted <tapted@chromium.org>
Reviewed-by: Dan Beam <dbeam@chromium.org>
Cr-Commit-Position: refs/heads/master@{#713343}

third_party/chaijs/README.chromium

 Name: Chai Assertion Library
 Short Name: chai
 URL: https://github.com/chaijs/chai
-Version: 3.4.1
-Revision: 12bfdd17648e2b3e11d64e5b926007a6d84bfbe8
-Date: Mon Nov 23 17:06:02 2015 +0000
+Version: 3.5.0
+Revision: 4ca0218391cf947c6cfac2d1a7424a63a4b4c232
+Date: Thu Jan 28 11:54:31 2016 +0000
 License: MIT
 License File: NOT_SHIPPED
 Security Critical: no
@@ -13,4 +13,6 @@ BDD / TDD assertion framework for node.js and the browser that can be
 paired with any testing framework.
 
 Local Modifications:
-Copied license text out of README.md.
+ - Copied license text out of README.md.
+ - Externs file from
+https://github.com/google/closure-compiler/tree/master/contrib/externs