Add default ctor to SkMask

src/core/SkDraw.cpp

Index: src/core/SkDraw.cpp
diff --git a/src/core/SkDraw.cpp b/src/core/SkDraw.cpp
index 7ebad61ddefa1dca87fb6b5efed388a165cc8a27..883359ca592c8a34a672b53afce442e4f81e3a6d 100644
--- a/src/core/SkDraw.cpp
+++ b/src/core/SkDraw.cpp
@@ -908,10 +908,8 @@ void SkDraw::drawDevMask(const SkMask& srcM, const SkPaint& paint) const {
 
     SkMask dstM;
     if (paint.getMaskFilter() &&
-            paint.getMaskFilter()->filterMask(&dstM, srcM, *fMatrix, nullptr)) {
+        paint.getMaskFilter()->filterMask(&dstM, srcM, *fMatrix, nullptr)) {
         mask = &dstM;
-    } else {
-        dstM.fImage = nullptr;
     }
     SkAutoMaskFreeImage ami(dstM.fImage);
 
@@ -2013,7 +2011,6 @@ static bool compute_bounds(const SkPath& devPath, const SkIRect* clipBounds,
 
         srcM.fBounds = *bounds;
         srcM.fFormat = SkMask::kA8_Format;
-        srcM.fImage = nullptr;
         if (!filter->filterMask(&dstM, srcM, *filterMatrix, &margin)) {
             return false;
         }