Blob Support

Currently I'm trying to use OpenLayers with AMP instead of google maps but besides having a problem with "publicPath", I'm also having a problem with Blob not being defined.

[amp-script] Uncaught ReferenceError: Blob is not defined

I get this error after finding a version of OpenLayers with 'publicPath: "" '.

I did a simple js with the only code being

`var blob = new Blob();`
`console.log(blob);`

And again I get the error that Blob is not defined

Reproduce the reported AMP worker-dom case with the minimal `new Blob()` script and confirm whether the failure is specific to the worker environment. Trace how worker-dom exposes DOM APIs and determine the scope of Blob support. Done means the example no longer raises `Blob is not defined` in the reported setup.

Written by the indexing model from the issue text.