change SkColorTable to be immutable

src/images/SkImageDecoder_libgif.cpp

 /*
  * Copyright 2006 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 "SkColor.h"
 #include "SkColorPriv.h"
@@ skipping 230 matching lines @@
                 return error_return(gif, *bm, "TopLeft");
             }
 
             // now we decode the colortable
             int colorCount = 0;
             {
                 const ColorMapObject* cmap = find_colormap(gif);
                 if (NULL == cmap) {
                     return error_return(gif, *bm, "null cmap");
                 }
+                colorCount = cmap->ColorCount;
 
-                colorCount = cmap->ColorCount;
-                SkAutoTMalloc<SkPMColor> colorStorage(colorCount);
-                SkPMColor* colorPtr = colorStorage.get();
+                SkPMColor colorPtr[256]; // storage for worst-case

[djsollen, 2013/10/09 15:42:18]

we should assert that colorCount is not greater than 256.

[reed1, 2013/10/09 15:51:25]

Done.

+                SkAlphaType alphaType = kOpaque_SkAlphaType;

[djsollen, 2013/10/09 15:42:18]

is it safe to assume always opaque without checking the reallyHasAlpha variable?

[reed1, 2013/10/09 15:51:25]

That is detected on line 266

                 for (int index = 0; index < colorCount; index++) {
                     colorPtr[index] = SkPackARGB32(0xFF,
                                                    cmap->Colors[index].Red,
                                                    cmap->Colors[index].Green,
                                                    cmap->Colors[index].Blue);
                 }
 
                 transpIndex = find_transpIndex(temp_save, colorCount);
                 bool reallyHasAlpha = transpIndex >= 0;
                 if (reallyHasAlpha) {
                     colorPtr[transpIndex] = SK_ColorTRANSPARENT; // ram in a transparent SkPMColor
+                    alphaType = kPremul_SkAlphaType;
                 }
 
-                SkAutoTUnref<SkColorTable> ctable(SkNEW_ARGS(SkColorTable, (colorPtr, colorCount)));
-                ctable->setIsOpaque(!reallyHasAlpha);
+                SkAutoTUnref<SkColorTable> ctable(SkNEW_ARGS(SkColorTable,
+                                                  (colorPtr, colorCount,
+                                                   alphaType)));
                 if (!this->allocPixelRef(bm, ctable)) {
                     return error_return(gif, *bm, "allocPixelRef");
                 }
             }
 
             const int innerWidth = desc.Width;
             const int innerHeight = desc.Height;
 
             // abort if either inner dimension is <= 0
             if (innerWidth <= 0 || innerHeight <= 0) {
@@ skipping 155 matching lines @@
 static SkImageDecoder_DecodeReg gReg(sk_libgif_dfactory);
 
 static SkImageDecoder::Format get_format_gif(SkStreamRewindable* stream) {
     if (is_gif(stream)) {
         return SkImageDecoder::kGIF_Format;
     }
     return SkImageDecoder::kUnknown_Format;
 }
 
 static SkImageDecoder_FormatReg gFormatReg(get_format_gif);