Re-enable Chrome for travis builds

[mramato]

Looks like the Chrome bug (or karma issue?) that prevented them from running is now fixed!

[cesium-concierge]

Thanks for the pull request @mramato!

• ✔️ Signed CLA found.
• ❔ CHANGES.md was not updated.
  • If this change updates the public API in any way, please add a bullet point to CHANGES.md.
• ❔ Unit tests were not updated.
  • Make sure you've updated tests to reflect your changes, added tests for any new code, and ran the code coverage tool.

Reviewers, don't forget to make sure that:

• Cesium Viewer works.
• Works in 2D/CV.
• Works (or fails gracefully) in IE11.

[mramato]

@OmarShehata can you hit merge on this?

[OmarShehata]

Looks good to me, thanks Matt!