harden requirements on SkBitmapCache

src/core/SkBitmapCache.cpp

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkBitmapCache.h"
 #include "SkResourceCache.h"
 #include "SkMipMap.h"
 #include "SkRect.h"
 
+SkBitmap::Allocator* SkBitmapCache::GetAllocator() {
+    return SkResourceCache::GetAllocator();
+}
+
 /**
  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();
     }
@@ skipping 61 matching lines @@
     BitmapKey key(src.getGenerationID(), invScaleX, invScaleY, get_bounds_from_bitmap(src));
     return find_and_return(key, result);
 }
 
 void SkBitmapCache::Add(const SkBitmap& src, SkScalar invScaleX, SkScalar invScaleY,
                         const SkBitmap& result) {
     if (0 == invScaleX || 0 == invScaleY) {
         // degenerate, and the key we use for mipmaps
         return;
     }
+    SkASSERT(result.isImmutable());
     SkResourceCache::Add(SkNEW_ARGS(BitmapRec, (src.getGenerationID(), invScaleX, invScaleY,
                                                 get_bounds_from_bitmap(src), result)));
 }
 
 bool SkBitmapCache::Find(uint32_t genID, int width, int height, SkBitmap* result) {
     BitmapKey key(genID, SK_Scalar1, SK_Scalar1, SkIRect::MakeWH(width, height));
     return find_and_return(key, result);
 }
 
 void SkBitmapCache::Add(uint32_t genID, int width, int height, const SkBitmap& result) {
+    SkASSERT(result.isImmutable());
     SkResourceCache::Add(SkNEW_ARGS(BitmapRec, (genID, SK_Scalar1, SK_Scalar1,
                                                 SkIRect::MakeWH(width, height), result)));
 }
 
 //////////////////////////////////////////////////////////////////////////////////////////
 
 struct MipMapRec : public SkResourceCache::Rec {
     MipMapRec(const SkBitmap& src, const SkMipMap* result)
         : fKey(src.getGenerationID(), 0, 0, get_bounds_from_bitmap(src))
         , fMipMap(SkRef(result))
@@ skipping 21 matching lines @@
     }
     return result;
 }
 
 void SkMipMapCache::Add(const SkBitmap& src, const SkMipMap* result) {
     if (result) {
         SkResourceCache::Add(SkNEW_ARGS(MipMapRec, (src, result)));
     }
 }