The original implementation tries to intercept events from the chart internal iframe, which ones failing on Chrome 60. Checking internals doesn't seem the best approach, instead we could consider that a chart has been resized after the resize method has been called and processed. So let's hook `Chart.resize` and callback once it's done.
`instanceof HTMLCanvasElement/CanvasRenderingContext2D` fails when the item is inside an iframe or when running in a protected environment. We could guess the types from their toString() value but let's keep things flexible and assume it's a sufficient condition if the item has a context2D which has item as `canvas`.
`karma.conf.ci.js` has been merged into `karma.conf.js` for local testing consistency: `gulp unittestWatch` has been replaced by `gulp unittest --watch` and thus use exactly the same config file. Upgrade to latest jasmine and karma packages and remove deprecated `gulp-karma` dependency (directly use `karma.Server` in gulp).
Split `test/mockContext.js` into smaller `test/jasmine.*` modules to make easier unit tests maintenance and finally, move all `*.test.js` files under the `test/specs` folder.
