Skip memcpy() swizzles in SkPngCodec

src/codec/SkPngCodec.h

Index: src/codec/SkPngCodec.h
diff --git a/src/codec/SkPngCodec.h b/src/codec/SkPngCodec.h
index 95fd61316342f5f46dd875f724e3df755b34b6ca..0989754789b7a7316e194f29fe87a233afc8b700 100644
--- a/src/codec/SkPngCodec.h
+++ b/src/codec/SkPngCodec.h
@@ -38,6 +38,7 @@ protected:
                               SkPMColor*, int* ctableCount);
     SkSampler* getSampler(bool createIfNecessary) override {
         SkASSERT(fSwizzler);
+        fInPlaceSwizzle = false;

[msarett, 2016/02/05 20:48:18]

Problem:

Here we assume that the client is calling getSampler() in order to call
setSampleSize() next (in which case we can't swizzle in place).

This is weird and unnecessarily pessimistic.

         return fSwizzler;
     }
 
@@ -47,6 +48,7 @@ protected:
     SkSwizzler* swizzler() { return fSwizzler; }
     SkSwizzler::SrcConfig srcConfig() const { return fSrcConfig; }
     int numberPasses() const { return fNumberPasses; }
+    bool inPlaceSwizzle() { return fInPlaceSwizzle; }
 
 private:
     SkAutoTUnref<SkPngChunkReader>  fPngChunkReader;
@@ -60,6 +62,7 @@ private:
     SkSwizzler::SrcConfig           fSrcConfig;
     const int                       fNumberPasses;
     int                             fBitDepth;
+    bool                            fInPlaceSwizzle;
 
     bool decodePalette(bool premultiply, int* ctableCount);
     void destroyReadStruct();