Make swizzling in read/write pixel copy code more generic

src/gpu/effects/GrConfigConversionEffect.h

Index: src/gpu/effects/GrConfigConversionEffect.h
diff --git a/src/gpu/effects/GrConfigConversionEffect.h b/src/gpu/effects/GrConfigConversionEffect.h
index 56beef97b192fa820a6f06264fc312fc5ddc7cef..65c55e78b6e76ba234f5d6712a7dffd26eddfa1b 100644
--- a/src/gpu/effects/GrConfigConversionEffect.h
+++ b/src/gpu/effects/GrConfigConversionEffect.h
@@ -9,14 +9,14 @@
 #define GrConfigConversionEffect_DEFINED
 
 #include "GrSingleTextureEffect.h"
+#include "GrSwizzle.h"
 
 class GrInvariantOutput;
 
 /**
  * This class is used to perform config conversions. Clients may want to read/write data that is
- * unpremultiplied. Also on some systems reading/writing BGRA or RGBA is faster. In those cases we
- * read/write using the faster path and perform an R/B swap in the shader if the client data is in
- * the slower config.
+ * unpremultiplied. Additionally, the channels may also be swizzled for optimal readback/upload
+ * performance.
  */
 class GrConfigConversionEffect : public GrSingleTextureEffect {
 public:
@@ -33,12 +33,12 @@ public:
         kPMConversionCnt
     };
 
-    static const GrFragmentProcessor* Create(GrTexture*, bool swapRedAndBlue, PMConversion,
+    static const GrFragmentProcessor* Create(GrTexture*, const GrSwizzle&, PMConversion,
                                              const SkMatrix&);
 
     const char* name() const override { return "Config Conversion"; }
 
-    bool swapsRedAndBlue() const { return fSwapRedAndBlue; }
+    const GrSwizzle& swizzle() const { return fSwizzle; }
     PMConversion  pmConversion() const { return fPMConversion; }
 
     // This function determines whether it is possible to choose PM->UPM and UPM->PM conversions
@@ -52,7 +52,7 @@ public:
 
 private:
     GrConfigConversionEffect(GrTexture*,
-                             bool swapRedAndBlue,
+                             const GrSwizzle&,
                              PMConversion pmConversion,
                              const SkMatrix& matrix);
 
@@ -64,7 +64,7 @@ private:
 
     void onComputeInvariantOutput(GrInvariantOutput* inout) const override;
 
-    bool            fSwapRedAndBlue;
+    GrSwizzle       fSwizzle;
     PMConversion    fPMConversion;
 
     GR_DECLARE_FRAGMENT_PROCESSOR_TEST;