DevTools: Do not lint front_end/protocol_externs.js.

This file seems to be autogenerated and currently produces ~1k eslint errors.

BUG=none
R=chenwilliam

Review-Url: https://codereview.chromium.org/2566553002
Cr-Commit-Position: refs/heads/master@{#437991}

AUTHORS

@@ -392,6 +392,7 @@ Kirill Bobyrev <kirillbobyrev@gmail.com>
 Kirk Shoop <kirk.shoop@microsoft.com>
 Kihwang Kim <pwangkk@gmail.com>
 Klemen Forstnerič <klemen.forstneric@gmail.com>
+Konrad Dzwinel <kdzwinel@gmail.com>
 Krishna Chaitanya <krish.botta@samsung.com>
 Kristof Kosztyo <kkosztyo.u-szeged@partner.samsung.com>
 Krzysztof Czech <k.czech@samsung.com>

third_party/WebKit/Source/devtools/.eslintignore

@@ -9,3 +9,4 @@ front_end/gonzales/*
 front_end/InspectorBackendCommands.js
 front_end/SupportedCSSProperties.js
 front_end/terminal/xterm.js/**
+front_end/protocol_externs.js