O(1) SkPictureUtils::ApproxBytesUsed()

src/core/SkVarAlloc.h

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkVarAlloc_DEFINED
 #define SkVarAlloc_DEFINED
 
@@ skipping 17 matching lines @@
         }
         SkASSERT(bytes <= fRemaining);
 
         char* ptr = fByte;
         fByte += bytes;
         fRemaining = SkToU32(fRemaining - bytes);
         return ptr;
     }
 
     // Returns our best estimate of the number of bytes we've allocated.
-    // (We intentionally do not track this precisely to save space.)
-    size_t approxBytesAllocated() const;
+    // (We may not track this precisely to save space.)
+    size_t approxBytesAllocated() const { return fBytesAllocated; }
 
 private:
     void makeSpace(size_t bytes, unsigned flags);
 
+    size_t fBytesAllocated;
+
     char* fByte;
     unsigned fRemaining;
     unsigned fLgSize;
 
     struct Block;
     Block* fBlock;
 };
-SK_COMPILE_ASSERT(sizeof(SkVarAlloc) <= 24, SkVarAllocSize);
+SK_COMPILE_ASSERT(sizeof(SkVarAlloc) <= 32, SkVarAllocSize);
 
 #endif//SkVarAlloc_DEFINED