Auto merge of #41 - dzbarsky:read_pixels, r=emilio
Auto merge of #41 - dzbarsky:read_pixels, r=emilio

Read pixels

alanamramjit/webrender,servo/webrender,servo/webrender,servo/webrender,DDEFISHER/webrender_traits,servo/webrender,servo/webrender,alanamramjit/webrender,servo/webrender,servo/webrender_traits