Fix memory leak in filterRRectToNine

src/effects/SkBlurMaskFilter.cpp

Index: src/effects/SkBlurMaskFilter.cpp
===================================================================
--- src/effects/SkBlurMaskFilter.cpp	(revision 12220)
+++ src/effects/SkBlurMaskFilter.cpp	(working copy)
@@ -333,6 +333,8 @@
         return kFalse_FilterReturn;
     }
 
+    SkAutoMaskFreeImage amf(srcM.fImage);
+
     if (!this->filterMask(&patch->fMask, srcM, matrix, &margin)) {
         return kFalse_FilterReturn;
     }