Change description:
Implement Float32ImageData

Changes to API surface:
 - Provides new API to create and manipulate Float32ImageData.
 - The API is very similar to the current ImageData, plus color management added to the constructors/getters/setters.

Links:
Public standards discussion: https://github.com/whatwg/html/issues/299
Proposal: https://github.com/junov/CanvasColorSpace/blob/master/CanvasColorSpaceProposal.md#imagedata

Support in other browsers:
Internet Explorer: No
Edge: No
Safari: No
Firefox: No
Safari: No