return reference to cache instead of copying the mask

src/core/SkMask.cpp

 /*
  * Copyright 2007 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 "SkMask.h"
 
+//#define TRACK_SKMASK_LIFETIME
+
 /** returns the product if it is positive and fits in 31 bits. Otherwise this
     returns 0.
  */
 static int32_t safeMul32(int32_t a, int32_t b) {
     int64_t size = sk_64_mul(a, b);
     if (size > 0 && sk_64_isS32(size)) {
         return sk_64_asS32(size);
     }
     return 0;
 }
 
 size_t SkMask::computeImageSize() const {
     return safeMul32(fBounds.height(), fRowBytes);
 }
 
 size_t SkMask::computeTotalImageSize() const {
     size_t size = this->computeImageSize();
     if (fFormat == SkMask::k3D_Format) {
         size = safeMul32(SkToS32(size), 3);
     }
     return size;
 }
 
+#ifdef TRACK_SKMASK_LIFETIME
+    static int gCounter;
+#endif
+
 /** We explicitly use this allocator for SkBimap pixels, so that we can
     freely assign memory allocated by one class to the other.
 */
 uint8_t* SkMask::AllocImage(size_t size) {
+#ifdef TRACK_SKMASK_LIFETIME
+    SkDebugf("SkMask::AllocImage %d\n", gCounter++);
+#endif
     return (uint8_t*)sk_malloc_throw(SkAlign4(size));
 }
 
 /** We explicitly use this allocator for SkBimap pixels, so that we can
     freely assign memory allocated by one class to the other.
 */
 void SkMask::FreeImage(void* image) {
+#ifdef TRACK_SKMASK_LIFETIME
+    if (image) {
+        SkDebugf("SkMask::FreeImage  %d\n", --gCounter);
+    }
+#endif
     sk_free(image);
 }
 
 ///////////////////////////////////////////////////////////////////////////////
 
 static const int gMaskFormatToShift[] = {
     ~0, // BW -- not supported
     0,  // A8
     0,  // 3D
     2,  // ARGB32
     1,  // LCD16
 };
 
 static int maskFormatToShift(SkMask::Format format) {
     SkASSERT((unsigned)format < SK_ARRAY_COUNT(gMaskFormatToShift));
     SkASSERT(SkMask::kBW_Format != format);
     return gMaskFormatToShift[format];
 }
 
 void* SkMask::getAddr(int x, int y) const {
     SkASSERT(kBW_Format != fFormat);
     SkASSERT(fBounds.contains(x, y));
     SkASSERT(fImage);
 
     char* addr = (char*)fImage;
     addr += (y - fBounds.fTop) * fRowBytes;
     addr += (x - fBounds.fLeft) << maskFormatToShift(fFormat);
     return addr;
 }