detach blur result texture when it is the same texture used to render path mask

gyp/gmslides.gypi

 # include this gypi to include all the golden master slides.
 {
   'sources': [
     '../gm/aaclip.cpp',
     '../gm/aarectmodes.cpp',
     '../gm/alphagradients.cpp',
     '../gm/androidfallback.cpp',
     '../gm/arcofzorro.cpp',
     '../gm/arithmode.cpp',
     '../gm/beziereffects.cpp',
@@ skipping 97 matching lines @@
     '../gm/samplerstress.cpp',
     # '../gm/scalebitmap.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/skbug1719.cpp',
     '../gm/stringart.cpp',
     '../gm/spritebitmap.cpp',
     '../gm/srcmode.cpp',
     '../gm/strokefill.cpp',
     '../gm/strokerect.cpp',
     '../gm/strokerects.cpp',
     '../gm/strokes.cpp',
     '../gm/tablecolorfilter.cpp',
     '../gm/texteffects.cpp',
     '../gm/testimagefilters.cpp',
@@ skipping 14 matching lines @@
     '../gm/xfermodes2.cpp',
     '../gm/xfermodes3.cpp',
   ],
 }
 
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