Feature : Support ArrayBuffer with js bindings

[elliotwoods]

In order to tidily support passing binary data (e.g. live image data) between python and js sides (e.g. for computer vision workflows), it would be great to able to support native js/python binary types.

Ideally, this would mean we could:

• [Python calls JS function] Pass a binary array or memory buffer as an argument. Receive an ArrayBuffer
• [JS calls Python function] Pass an ArrayBuffer, receive a binary array

Issue discussed on forum at:
https://groups.google.com/forum/#!topic/cefpython/Uc3n44cpkbo

[cztomczak]

For implementation details see this comment by Marshall on the CEF forum:

There is no API currently for extracting an ArrayBuffer value via CefV8Value. Where is the ArrayBuffer coming from? If the data is small you can convert it to a string before passing it to the bound JS function. If the data is large it will be more efficient to send via the network stack (using XMLHttpRequest, for example), like in https://bitbucket.org/chromiumembedded/cef/wiki/GeneralUsage.md#markdown-header-request-handling

Ref: https://magpcss.org/ceforum/viewtopic.php?p=39218#p39218

Update: CEF provides CefBinaryValue as part of CefV8Value, see: https://github.com/chromiumembedded/cef/blob/ea0e213bef0367edfedb7cf0a487e04e8c6cdf00/include/cef_values.h#L233