add isSimilarityTransform() and some tests
add isSimilarityTransform() and some tests

Committed on behalf of Guanqun.Lu@gmail.com

Review URL: http://codereview.appspot.com/5999050/




git-svn-id: e8541e15acce502a64c929015570ad1648e548cd@3681 2bbb7eff-a529-9590-31e7-b0007b416f81

mrobinson/skia,Cue/skia,Cue/skia,metajack/skia,mrobinson/skia,metajack/skia,Cue/skia,mrobinson/skia,mrobinson/skia,Cue/skia,metajack/skia,mrobinson/skia,metajack/skia