Texture compression unit tests along with a couple of bug fixes

src/utils/SkTextureCompressor.cpp

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkTextureCompressor.h"
 
 #include "SkBitmap.h"
@@ skipping 91 matching lines @@
     palettes[1][6] = 0;
     palettes[1][7] = 255;
 
     // Figure out which of the two is better:
     //  -  accumError holds the accumulated error for each pixel from
     //     the associated palette
     //  -  indices holds the best indices for each palette in the
     //     bottom 48 (16*3) bits.
     uint32_t accumError[2] = { 0, 0 };
     uint64_t indices[2] = { 0, 0 };
-    for (int i = 15; i >= 0; ++i) {
+    for (int i = 15; i >= 0; --i) {
         // For each palette:
         // 1. Retreive the result of this pixel
         // 2. Store the error in accumError
         // 3. Store the minimum palette index in indices.
         for (int p = 0; p < 2; ++p) {
             uint32_t result = compute_error(block[i], palettes[p]);
             accumError[p] += (result >> 8);
             indices[p] <<= 3;
-            indices[p] |= result & ~7;
+            indices[p] |= result & 7;
         }
     }
 
     SkASSERT(indices[0] < (static_cast<uint64_t>(1) << 48));
     SkASSERT(indices[1] < (static_cast<uint64_t>(1) << 48));
 
     uint8_t paletteIdx = (accumError[0] > accumError[1]) ? 0 : 1;
 
     // Assemble the compressed block.
     uint64_t result = 0;
@@ skipping 52 matching lines @@
     return SkData::NewFromMalloc(dst, compressedDataSize);
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 
 namespace SkTextureCompressor {
 
 typedef SkData *(*CompressBitmapProc)(const SkBitmap &bitmap);
 
 SkData *CompressBitmapToFormat(const SkBitmap &bitmap, Format format) {
+    SkAutoLockPixels alp(bitmap);
+
     CompressBitmapProc kProcMap[kLastEnum_SkColorType + 1][kFormatCnt];
     memset(kProcMap, 0, sizeof(kProcMap));
 
     // Map available bitmap configs to compression functions
     kProcMap[SkBitmap::kA8_Config][kLATC_Format] = compress_a8_to_latc;
 
     CompressBitmapProc proc = kProcMap[bitmap.colorType()][format];
     if (NULL != proc) {
         return proc(bitmap);
     }
 
     return NULL;
 }
 
 }  // namespace SkTextureCompressor