Prioritise AMD module definition

[merih]

In environments like electron, module['exports'] could also be available, when the website code is using AMD. Previous module definition code was preventing dialog polyfill from being defined as an AMD module in electron since it was cheking CJS module availability first, this PR prioritises AMD definition.

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[googlebot]

Thanks for your pull request. It looks like this may be your first contribution to a Google open source project. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

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[merih]

I signed it!

[googlebot]

CLAs look good, thanks!

[googlebot]

CLAs look good, thanks!

[samthor]

LGTM