After r88913, the client area of extension panels is truncated to 150px in height. This is due to that parent element does not have length: set explicitly (uses position: absolute; top: 0; bottom: 0) and height: 100% on the iframe is actually treated as height: auto;
Created attachment 98375 [details] patch
Manually committed r89659: http://trac.webkit.org/changeset/89659