Added missing MouseEvent constructor.

[dperelman]

Documented here: https://developer.mozilla.org/en-US/docs/Web/API/MouseEvent/MouseEvent

Fixes #674.

[msftclas]

Hi @dperelman, I'm your friendly neighborhood Microsoft Pull Request Bot (You can call me MSBOT). Thanks for your contribution!

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[mhegazy]

Thanks for the PR. this file is auto generated form IE's dom specifications and we do not hand author it. Any changes we make to the file will be removed next time we auto generate it, and managing these manual changes can get hairy. We are in the process of rewiring the generation process so we will be able to take these changes then. can you log an issue to track the missing parameters so that we can revisit it once the new auto-generation script is available.

[dperelman]

Okay. The issue already exists. It's #674, which I mentioned in the inital pull request.