Make swizzling in read/write pixel copy code more generic

include/gpu/GrContext.h

Index: include/gpu/GrContext.h
diff --git a/include/gpu/GrContext.h b/include/gpu/GrContext.h
index b60aea08130a618b98525cdcf3e661d66dd686f8..00a92836c513d6ef9963cc9d3ca925101a2a489a 100644
--- a/include/gpu/GrContext.h
+++ b/include/gpu/GrContext.h
@@ -43,6 +43,7 @@ class GrTextContext;
 class GrTextureParams;
 class GrVertexBuffer;
 class GrStrokeInfo;
+class GrSwizzle;
 class SkTraceMemoryDump;
 
 class SK_API GrContext : public SkRefCnt {
@@ -429,11 +430,11 @@ private:
     /**
      * These functions create premul <-> unpremul effects if it is possible to generate a pair
      * of effects that make a readToUPM->writeToPM->readToUPM cycle invariant. Otherwise, they
-     * return NULL.
+     * return NULL. They also can perform a swizzle as part of the draw.
      */
-    const GrFragmentProcessor* createPMToUPMEffect(GrTexture*, bool swapRAndB,
+    const GrFragmentProcessor* createPMToUPMEffect(GrTexture*, const GrSwizzle&,
                                                    const SkMatrix&) const;
-    const GrFragmentProcessor* createUPMToPMEffect(GrTexture*, bool swapRAndB,
+    const GrFragmentProcessor* createUPMToPMEffect(GrTexture*, const GrSwizzle&,
                                                    const SkMatrix&) const;
     /** Called before either of the above two functions to determine the appropriate fragment
         processors for conversions. This must be called by readSurfacePixels before a mutex is