Delete dead BitmapRegionDecoder code in tools

tools/SkBitmapRegionSampler.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 "SkBitmapRegionSampler.h"
-#include "SkCodecPriv.h"
-
-SkBitmapRegionSampler::SkBitmapRegionSampler(SkImageDecoder* decoder, int width, 
-                                             int height)
-    : INHERITED(width, height)
-    , fDecoder(decoder)
-{}
-
-bool SkBitmapRegionSampler::decodeRegion(SkBitmap* bitmap, SkBitmap::Allocator* allocator,
-        const SkIRect& desiredSubset, int sampleSize, SkColorType colorType, bool requireUnpremul) {
-    fDecoder->setDitherImage(true);
-    fDecoder->setPreferQualityOverSpeed(false);
-    fDecoder->setRequireUnpremultipliedColors(false);
-    fDecoder->setSampleSize(sampleSize);
-    fDecoder->setAllocator(allocator);
-
-    // kAlpha8 is the legacy representation of kGray8 used by SkImageDecoder
-    if (kGray_8_SkColorType == colorType) {
-        colorType = kAlpha_8_SkColorType;
-    }
-
-    bool result = fDecoder->decodeSubset(bitmap, desiredSubset, colorType);
-    fDecoder->setAllocator(nullptr);
-    return result;
-}