Unable to create 2D/GL/Audio context under Node.js

[Siorki]

When attempting to hash the methods for 2D / WebGL / Audio context, an instance of that context is created and used to enumerate methods and properties thereof.

This does not work when run with Node.js - server-side js does not know about Canvas, rendering context nor Audio context, since all of these are usually client-side operations.

Upon attempting to create a canvas (for 2D or WebGL context)

ReferenceError: document is not defined
    at Object.ShapeShifter.preprocess (shapeShifter.js:75:17)

Upon attempting to create an AudioContext

ReferenceError: AudioContext is not defined
    at Object.ShapeShifter.preprocess (shapeShifter.js:115:22)

[Siorki]

There are implementations of Canvas under node, such as node-canvas, however they may or may not have exactly the same methods as the canvas found in browsers (and even these differ, see #20). Sometimes they offer more methods, or implement them in advance of the spec.
Unfortunately, one needs a similar result whether RegPack is run in a browser or with node.js

[Siorki]

Proposed solution : introduce a class named ContextDescriptor, in charge of building a list of context properties, methods and constat values, with different implementations :

• under a browser, it lists methods and properties of real instances of the appropriate context
• under Node, it uses hardcoded lists, which were derived from browsers implementations. These need to be updated whenever a browser introduces a new method in these contexts.

I am not exactly satisfied with that, even though there is no relevant alternative (node-canvas and other implementations suffer the same drawbacks). This design will at least allow for easy replacement of the ContextDescriptor implementation should a better solution arise.