Avoid regenerating cached textblobs on integer scrolls

src/gpu/GrMemoryPool.h

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrMemoryPool_DEFINED
 #define GrMemoryPool_DEFINED
 
@@ skipping 25 matching lines @@
     /**
      * p must have been returned by allocate()
      */
     void release(void* p);
 
     /**
      * Returns true if there are no unreleased allocations.
      */
     bool isEmpty() const { return fTail == fHead && !fHead->fLiveCount; }
 
+    /**
+     * Returns the total allocated size of the GrMemoryPool
+     */
+    size_t size() const { return fSize; }
+
 private:
     struct BlockHeader;
 
     static BlockHeader* CreateBlock(size_t size);
 
     static void DeleteBlock(BlockHeader* block);
 
     void validate();
 
     struct BlockHeader {
         BlockHeader* fNext;      ///< doubly-linked list of blocks.
         BlockHeader* fPrev;
         int          fLiveCount; ///< number of outstanding allocations in the
                                  ///< block.
         intptr_t     fCurrPtr;   ///< ptr to the start of blocks free space.
         intptr_t     fPrevPtr;   ///< ptr to the last allocation made
         size_t       fFreeSize;  ///< amount of free space left in the block.
+        size_t       fSize;      ///< total allocated size of the block
     };
 
     enum {
         // We assume this alignment is good enough for everybody.
         kAlignment    = 8,
         kHeaderSize   = GR_CT_ALIGN_UP(sizeof(BlockHeader), kAlignment),
         kPerAllocPad  = GR_CT_ALIGN_UP(sizeof(BlockHeader*), kAlignment),
     };
+    size_t                            fSize;
     size_t                            fPreallocSize;
     size_t                            fMinAllocSize;
     BlockHeader*                      fHead;
     BlockHeader*                      fTail;
 #ifdef SK_DEBUG
     int                               fAllocationCnt;
+    int                               fAllocBlockCnt;
 #endif
 };
 
 #endif