extend bitmaprect bench to include drawing with non-opaque alpha git-svn-id: http://skia.googlecode.com/svn/trunk@5965 2bbb7eff-a529-9590-31e7-b0007b416f81
git-svn-id: http://skia.googlecode.com/svn/trunk@5943 2bbb7eff-a529-9590-31e7-b0007b416f81
git-svn-id: http://skia.googlecode.com/svn/trunk@5915 2bbb7eff-a529-9590-31e7-b0007b416f81