Clean up unused or overly complex modes in SkSwizzler

src/codec/SkJpegCodec.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkCodec.h"
 #include "SkJpegCodec.h"
 #include "SkJpegDecoderMgr.h"
@@ skipping 311 matching lines @@
     }
 
     return kSuccess;
 }
 
 void SkJpegCodec::initializeSwizzler(const SkImageInfo& dstInfo, const Options& options) {
     SkSwizzler::SrcConfig srcConfig = SkSwizzler::kUnknown;
     if (JCS_CMYK == fDecoderMgr->dinfo()->out_color_space) {
         srcConfig = SkSwizzler::kCMYK;
     } else {
+        // If the out_color_space is not CMYK, the only reason we would need a swizzler is
+        // for sampling and/or subsetting.
         switch (dstInfo.colorType()) {
             case kGray_8_SkColorType:
-                srcConfig = SkSwizzler::kGray;
+                srcConfig = SkSwizzler::kNoOp8;
                 break;
-            case kRGBA_8888_SkColorType:
-                srcConfig = SkSwizzler::kRGBX;
-                break;
-            case kBGRA_8888_SkColorType:
-                srcConfig = SkSwizzler::kBGRX;
+            case kN32_SkColorType:
+                srcConfig = SkSwizzler::kNoOp32;
                 break;
             case kRGB_565_SkColorType:
-                srcConfig = SkSwizzler::kRGB_565;
+                srcConfig = SkSwizzler::kNoOp16;
                 break;
             default:
                 // This function should only be called if the colorType is supported by jpeg
                 SkASSERT(false);
         }
     }
 
     fSwizzler.reset(SkSwizzler::CreateSwizzler(srcConfig, nullptr, dstInfo, options));
     fStorage.reset(get_row_bytes(fDecoderMgr->dinfo()));
     fSrcRow = fStorage.get();
@@ skipping 91 matching lines @@
 #endif
 
 bool SkJpegCodec::onSkipScanlines(int count) {
     // Set the jump location for libjpeg errors
     if (setjmp(fDecoderMgr->getJmpBuf())) {
         return fDecoderMgr->returnFalse("setjmp");
     }
 
     return (uint32_t) count == jpeg_skip_scanlines(fDecoderMgr->dinfo(), count);
 }