Bug 899222 - Make about:home work via message passing (r=felipe)

--HG--
rename : browser/modules/AboutHomeUtils.jsm => browser/modules/AboutHome.jsm
Bug 904620 - Always send a transaction when we get a WebGL update to ensure that we get a composite. r=nrc
Bug 900133 - Don't mark textures as being sent to the compositor until after we've drawn to them. r=nical
Bug 900133 - Make sure we always set TEXTURE_DEALLOCATE_HOST when required. r=nical
Bug 900133 - Enable new textures on OSX. r=nical