Specify window size for the karma chrome launcher (Fixes #444)

[monfera]

Fixes #444 by specifying a certain window size for the Chrome launcher. The numbers are simply derived from observing the window size in the properly working case.

CI karma/jasmine testing isn't impacted because, while CI piggybacks on this baseline config file, it specifies a separate browser (currently, Firefox). @etpinard suggested we don't change CI starting options right now.

I haven't experienced any problems with the fact that the browser we use is named differently (we can't name it Chrome as it's wired to mean plain vanilla Chrome and is being referenced as the base.

[etpinard]

Nice solution.

This works like a charm on my machine.

@mdtusz @n-riesco @timelyportfolio could you try to pull this branch down and run:

 npm run test-jasmine -- tests/click_test.js

Thanks.

[n-riesco]

WFM (Executed 29 of 29 SUCCESS)

I've just looked into the PR; would this PR force us to use Chrome?

[mdtusz]

Works for me!

[etpinard]

Ok. Let's give a shot.