DevTools: Remove unused variables. Disallow unused variables with eslint

third_party/WebKit/Source/devtools/.eslintrc.js

 module.exports = {
     "root": true,
 
     "env": {
         "browser": true,
         "es6": true
     },
 
     /**
      * ESLint rules
@@ skipping 45 matching lines @@
         "no-cond-assign": 2,
         "no-debugger": 2,
         "no-console": [2, { "allow": ["warn", "error", "assert", "timeStamp", "time", "timeEnd"] }],
         "no-dupe-keys": 2,
         "no-duplicate-case": 2,
         "no-empty-character-class": 2,
         "no-unreachable": 2,
         "no-unsafe-negation": 2,
         "radix": 2,
         "valid-typeof": 2,
+        "no-unused-vars": [2, { "args": "none", "vars": "local" }],
 
         // es2015 features
         "require-yield": 2,
         "template-curly-spacing": [2, "never"],
 
         // spacing details
         "space-infix-ops": 2,
         "space-in-parens": [2, "never"],
         "space-before-function-paren": [2, "never"],
         "no-whitespace-before-property": 2,
@@ skipping 34 matching lines @@
             "afterColon": true,
             "align": "value"
         }],
         // quote-props is diabled, as property quoting styles are too varied to enforce.
         "quote-props": [0, "as-needed"],
 
         // no-implicit-globals will prevent accidental globals
         "no-implicit-globals": [0]
     }
 };