SkColorTable locking serves no purpose anymore.

src/images/SkImageDecoder_libpng.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 "SkImageDecoder.h"
 #include "SkImageEncoder.h"
 #include "SkColor.h"
@@ skipping 395 matching lines @@
         } else if (hasAlpha) {
             sc = SkScaledBitmapSampler::kRGBA;
         } else {
             sc = SkScaledBitmapSampler::kRGBX;
         }
 
         /*  We have to pass the colortable explicitly, since we may have one
             even if our decodedBitmap doesn't, due to the request that we
             upscale png's palette to a direct model
          */
-        SkAutoLockColors ctLock(colorTable);
-        if (!sampler.begin(decodedBitmap, sc, *this, ctLock.colors())) {
+        const SkPMColor* colors = colorTable ? colorTable->readColors() : NULL;
+        if (!sampler.begin(decodedBitmap, sc, *this, colors)) {
             return kFailure;
         }
         const int height = decodedBitmap->height();
 
         if (number_passes > 1) {
             SkAutoMalloc storage(origWidth * origHeight * srcBytesPerPixel);
             uint8_t* base = (uint8_t*)storage.get();
             size_t rowBytes = origWidth * srcBytesPerPixel;
 
             for (int i = 0; i < number_passes; i++) {
@@ skipping 459 matching lines @@
         } else if (hasAlpha) {
             sc = SkScaledBitmapSampler::kRGBA;
         } else {
             sc = SkScaledBitmapSampler::kRGBX;
         }
 
         /*  We have to pass the colortable explicitly, since we may have one
             even if our decodedBitmap doesn't, due to the request that we
             upscale png's palette to a direct model
          */
-        SkAutoLockColors ctLock(colorTable);
-        if (!sampler.begin(&decodedBitmap, sc, *this, ctLock.colors())) {
+        const SkPMColor* colors = colorTable ? colorTable->readColors() : NULL;
+        if (!sampler.begin(&decodedBitmap, sc, *this, colors)) {
             return false;
         }
         const int height = decodedBitmap.height();
 
         if (number_passes > 1) {
             SkAutoMalloc storage(origWidth * origHeight * srcBytesPerPixel);
             uint8_t* base = (uint8_t*)storage.get();
             size_t rb = origWidth * srcBytesPerPixel;
 
             for (int i = 0; i < number_passes; i++) {
@@ skipping 131 matching lines @@
 /*  Pack palette[] with the corresponding colors, and if hasAlpha is true, also
     pack trans[] and return the number of trans[] entries written. If hasAlpha
     is false, the return value will always be 0.
 
     Note: this routine takes care of unpremultiplying the RGB values when we
     have alpha in the colortable, since png doesn't support premul colors
 */
 static inline int pack_palette(SkColorTable* ctable,
                                png_color* SK_RESTRICT palette,
                                png_byte* SK_RESTRICT trans, bool hasAlpha) {
-    SkAutoLockColors alc(ctable);
-    const SkPMColor* SK_RESTRICT colors = alc.colors();
+    const SkPMColor* SK_RESTRICT colors = ctable ? ctable->readColors() : NULL;
     const int ctCount = ctable->count();
     int i, num_trans = 0;
 
     if (hasAlpha) {
         /*  first see if we have some number of fully opaque at the end of the
             ctable. PNG allows num_trans < num_palette, but all of the trans
             entries must come first in the palette. If I was smarter, I'd
             reorder the indices and ctable so that all non-opaque colors came
             first in the palette. But, since that would slow down the encode,
             I'm leaving the indices and ctable order as is, and just looking
@@ skipping 214 matching lines @@
     return SkImageDecoder::kUnknown_Format;
 }
 
 SkImageEncoder* sk_libpng_efactory(SkImageEncoder::Type t) {
     return (SkImageEncoder::kPNG_Type == t) ? SkNEW(SkPNGImageEncoder) : NULL;
 }
 
 static SkImageDecoder_DecodeReg gDReg(sk_libpng_dfactory);
 static SkImageDecoder_FormatReg gFormatReg(get_format_png);
 static SkImageEncoder_EncodeReg gEReg(sk_libpng_efactory);