Revert of df generation: single allocation with calloc

src/core/SkDistanceFieldGen.cpp

Index: src/core/SkDistanceFieldGen.cpp
diff --git a/src/core/SkDistanceFieldGen.cpp b/src/core/SkDistanceFieldGen.cpp
index 4f4de56a46f4c0d8282c7d427153be2536396bbe..30354e09f83cb783c49ee018af74b3d8e236b272 100755
--- a/src/core/SkDistanceFieldGen.cpp
+++ b/src/core/SkDistanceFieldGen.cpp
@@ -343,10 +343,15 @@
     int dataWidth = width + 2*pad;
     int dataHeight = height + 2*pad;
 
-    // create zeroed temp edge+DFData storage
-    SkAutoFree storage(sk_calloc_throw(dataWidth*dataHeight*(1 + sizeof(DFData))));
-    unsigned char* edgePtr = (unsigned char*)storage.get();
-    DFData*        dataPtr = (DFData*)(edgePtr + dataWidth*dataHeight);
+    // create temp data
+    size_t dataSize = dataWidth*dataHeight*sizeof(DFData);
+    SkAutoSMalloc<1024> dfStorage(dataSize);
+    DFData* dataPtr = (DFData*) dfStorage.get();
+    sk_bzero(dataPtr, dataSize);
+
+    SkAutoSMalloc<1024> edgeStorage(dataWidth*dataHeight*sizeof(char));
+    unsigned char* edgePtr = (unsigned char*) edgeStorage.get();
+    sk_bzero(edgePtr, dataWidth*dataHeight*sizeof(char));
 
     // copy glyph into distance field storage
     init_glyph_data(dataPtr, edgePtr, copyPtr,