Remove fake "browser" and "dom" modules

[lucaswoj]

This PR removes the fake "browser" and "dom" modules used in the test environment in favor of using the real modules with jsdom.

This is a follow-up to #3063

Checklist

• briefly describe the changes in this PR
• 🍏
• get a PR review 👍 / 👎

[jfirebaugh]

This description was specific to the browser version of browser.js, and can be removed or rewritten.

[jfirebaugh]

Can we merge this as-is and go for canvas, ajax, and web_worker in a followup PR? I'd like to write some Popup tests that require these changes.

[lucaswoj]

@jfirebaugh Sure! I'll fix this up and merge shortly.

[jfirebaugh]

The coverage dropped because the test-suite didn't run. This error did not fail the build:

/Users/distiller/mapbox-gl-js/test/suite_implementation.js:16
    browser.devicePixelRatio = options.pixelRatio;
                             ^

TypeError: Cannot set property devicePixelRatio of #<Object> which has only a getter
    at module.exports (/Users/distiller/mapbox-gl-js/test/suite_implementation.js:16:30)
    at /Users/distiller/mapbox-gl-js/node_modules/mapbox-gl-test-suite/lib/render.js:62:9
    at /Users/distiller/mapbox-gl-js/node_modules/mapbox-gl-test-suite/lib/harness.js:78:17
    at start (/Users/distiller/mapbox-gl-js/node_modules/mapbox-gl-test-suite/node_modules/queue-async/build/queue.js:35:43)
    at Server.<anonymous> (/Users/distiller/mapbox-gl-js/node_modules/mapbox-gl-test-suite/node_modules/queue-async/build/queue.js:48:24)
    at Server.g (events.js:260:16)
    at emitNone (events.js:67:13)
    at Server.emit (events.js:166:7)
    at emitListeningNT (net.js:1276:10)
    at nextTickCallbackWith1Arg (node.js:431:9)

[lucaswoj]

Test suite is failing because no fill outlines are being drawn but CI is still passing. This is a fun one 😂

[jfirebaugh]

set -e doesn't exit if the command that fails is part of a && list. 😢

[lucaswoj]

Easy fix! We weren't using the &&.

[lucaswoj]

Force pushed to resolve merge conflicts. This should be 🍏 and ready to 🚢 .