change offset to xy for pixelref subsetting

src/core/SkScaledImageCache.cpp

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkScaledImageCache.h"
 #include "SkMipMap.h"
 #include "SkOnce.h"
@@ skipping 351 matching lines @@
 
 /**
    This function finds the bounds of the bitmap *within its pixelRef*.
    If the bitmap lacks a pixelRef, it will return an empty rect, since
    that doesn't make sense.  This may be a useful enough function that
    it should be somewhere else (in SkBitmap?). */
 static SkIRect get_bounds_from_bitmap(const SkBitmap& bm) {
     if (!(bm.pixelRef())) {
         return SkIRect::MakeEmpty();
     }
-    size_t x, y;
-    SkTDivMod(bm.pixelRefOffset(), bm.rowBytes(), &y, &x);
-    x >>= bm.shiftPerPixel();
-    return SkIRect::MakeXYWH(x, y, bm.width(), bm.height());
+    SkIPoint origin = bm.pixelRefOrigin();
+    return SkIRect::MakeXYWH(origin.fX, origin.fY, bm.width(), bm.height());
 }
 
 
 SkScaledImageCache::ID* SkScaledImageCache::findAndLock(uint32_t genID,
                                                         int32_t width,
                                                         int32_t height,
                                                         SkBitmap* bitmap) {
     Rec* rec = this->findAndLock(genID, SK_Scalar1, SK_Scalar1,
                                  SkIRect::MakeWH(width, height));
     if (rec) {
@@ skipping 408 matching lines @@
     return SkScaledImageCache::GetBytesUsed();
 }
 
 size_t SkGraphics::GetImageCacheByteLimit() {
     return SkScaledImageCache::GetByteLimit();
 }
 
 size_t SkGraphics::SetImageCacheByteLimit(size_t newLimit) {
     return SkScaledImageCache::SetByteLimit(newLimit);
 }