Clean up unused or overly complex modes in SkSwizzler

src/codec/SkSwizzler.h

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkSwizzler_DEFINED
 #define SkSwizzler_DEFINED
 
 #include "SkCodec.h"
 #include "SkColor.h"
 #include "SkImageInfo.h"
 #include "SkSampler.h"
 
 class SkSwizzler : public SkSampler {
 public:
     /**
      *  Enum describing the config of the source data.
      */
     enum SrcConfig {
         kUnknown,  // Invalid type.
-        kBit,      // A single bit to distinguish between white and black
+        kBit,      // A single bit to distinguish between white and black.
         kGray,
         kIndex1,
         kIndex2,
         kIndex4,
         kIndex,
         kRGB,
         kBGR,
-        kRGBX,
-        kBGRX,
+        kBGRX,     // The alpha channel can be anything, but the image is opaque.
         kRGBA,
         kBGRA,
-        kRGB_565,
         kCMYK,
+        kNoOp8,    // kNoOp modes are used exclusively for sampling, subsetting, and
+        kNoOp16,   // copying.  The pixels themselves do not need to be modified.
+        kNoOp32,
     };
 
     /*
      *
      * Returns bits per pixel for source config
      *
      */
     static int BitsPerPixel(SrcConfig sc) {
         switch (sc) {
             case kBit:
             case kIndex1:
                 return 1;
             case kIndex2:
                 return 2;
             case kIndex4:
                 return 4;
             case kGray:
             case kIndex:
+            case kNoOp8:
                 return 8;
-            case kRGB_565:
+            case kNoOp16:
                 return 16;
             case kRGB:
             case kBGR:
                 return 24;
-            case kRGBX:
             case kRGBA:
             case kBGRX:
             case kBGRA:
             case kCMYK:
+            case kNoOp32:
                 return 32;
             default:
                 SkASSERT(false);
                 return 0;
         }
     }
 
     /*
      *
      * Returns bytes per pixel for source config
@@ skipping 174 matching lines @@
                                           //     fBPP is bitsPerPixel
     const int           fDstBPP;          // Bytes per pixel for the destination color type
 
     SkSwizzler(RowProc fastProc, RowProc proc, const SkPMColor* ctable, int srcOffset,
             int srcWidth, int dstOffset, int dstWidth, int srcBPP, int dstBPP);
 
     int onSetSampleX(int) override;
 
 };
 #endif // SkSwizzler_DEFINED