Register Two_Point_Conical_Gradient for flattening.

Without being registered, the twopointconical GM fails
when using --pipe or --serialize, since this gradient
will not be flattened/unflattened.
Review URL: https://codereview.appspot.com/6294060

git-svn-id: http://skia.googlecode.com/svn/trunk@4226 2bbb7eff-a529-9590-31e7-b0007b416f81
1 file changed