[e] (0) Clarify rules for drawing focus rings
Affected topics: Canvas

git-svn-id: http://svn.whatwg.org/webapps@8227 340c8d12-0b0e-0410-8428-c7bf67bfef74
[giow] (3) Clarify how to handle zero-width <img>s in drawImage(), and make zero-width <canvas>es not throw.
Affected topics: Canvas

git-svn-id: http://svn.whatwg.org/webapps@8228 340c8d12-0b0e-0410-8428-c7bf67bfef74