gm self-test: use a pathologically simple test case instead of dashing2

gyp/gmslides.gypi

 # include this gypi to include all the golden master slides.
 {
   'sources': [
     '../gm/aaclip.cpp',
     '../gm/aarectmodes.cpp',
     '../gm/arithmode.cpp',
     '../gm/bicubicfilter.cpp',
     '../gm/bigmatrix.cpp',
     '../gm/bitmapcopy.cpp',
     '../gm/bitmapmatrix.cpp',
@@ skipping 50 matching lines @@
     '../gm/pathfill.cpp',
     '../gm/pathinterior.cpp',
     '../gm/pathreverse.cpp',
     '../gm/points.cpp',
     '../gm/poly2poly.cpp',
     '../gm/quadpaths.cpp',
     '../gm/rrect.cpp',
     '../gm/rrects.cpp',
     '../gm/samplerstress.cpp',
     '../gm/shaderbounds.cpp',
+    '../gm/selftest.cpp',
     '../gm/shadertext.cpp',
     '../gm/shadertext2.cpp',
     '../gm/shadertext3.cpp',
     '../gm/shadows.cpp',
     '../gm/shallowgradient.cpp',
     '../gm/simpleaaclip.cpp',
     '../gm/spritebitmap.cpp',
     '../gm/srcmode.cpp',
     '../gm/strokefill.cpp',
     '../gm/strokerect.cpp',
@@ skipping 12 matching lines @@
     '../gm/verylargebitmap.cpp',
     '../gm/xfermodes.cpp',
   ],
 }
 
 # Local Variables:
 # tab-width:2
 # indent-tabs-mode:nil
 # End:
 # vim: set expandtab tabstop=2 shiftwidth=2: