Adding support to bitmaprenderer in OffscreenCanvas

Registering the factory on OffscreenCanvas in modules, adding
ImageBitmapRenderer to the union type for OffscreenCanvas.
Adding new functionality to bitmaprenderer to let it be used
in offscreencanvas.
Changing IDL and some tests to validate new functionality.
Adding a new virtual test to guarantee testing validation
of trasnsfertooffscreencanvas for bitmaprenderer.


Intent to ship: https://groups.google.com/a/chromium.org/forum/#!topic/blink-dev/ufFQ4OvtqxQ

Bug: 907141
Change-Id: Ibcac820288bab336a1cf01b528eb3f41ece9c832
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1483831
Commit-Queue: Juanmi Huertas <juanmihd@chromium.org>
Reviewed-by: Chris Harrelson <chrishtr@chromium.org>
Reviewed-by: Fernando Serboncini <fserb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#663341}
48 files changed