Image decoder fixes (mostly) around A8.

src/images/SkScaledBitmapSampler.cpp

 /*
  * Copyright 2007 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 #include "SkScaledBitmapSampler.h"
 #include "SkBitmap.h"
@@ skipping 531 matching lines @@
     }
     // Ignore dither and skip zeroes
     return Sample_Index_DI;
 }
 
 // A8
 static bool Sample_Gray_DA8(void* SK_RESTRICT dstRow,
                             const uint8_t* SK_RESTRICT src,
                             int width, int deltaSrc, int,
                             const SkPMColor[]) {
-    memcpy(dstRow, src, width);
+    // Sampling Gray to A8 uses the same function as Index to Index8,
+    // except we assume that there is alpha for speed, since an A8
+    // bitmap with no alpha is not interesting.
+    (void) Sample_Index_DI(dstRow, src, width, deltaSrc, /* y unused */ 0,
+                           /* ctable unused */ NULL);
     return true;
 }
 
 static SkScaledBitmapSampler::RowProc get_gray_to_A8_proc(const SkImageDecoder& decoder) {
     if (decoder.getRequireUnpremultipliedColors()) {
         return NULL;
     }
     // Ignore skip and dither.
     return Sample_Gray_DA8;
 }
@@ skipping 276 matching lines @@
                     SkScaledBitmapSampler::RowProc actual = RowProcTester::getRowProc(sampler);
                     SkASSERT(expected == actual);
                     procCounter++;
                 }
             }
         }
     }
     SkASSERT(SK_ARRAY_COUNT(gTestProcs) == procCounter);
 }
 #endif // SK_DEBUG