Use SkNVRefCnt for a couple common types.

include/core/SkTextBlob.h

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkTextBlob_DEFINED
 #define SkTextBlob_DEFINED
 
 #include "../private/SkTemplates.h"
 #include "SkPaint.h"
 #include "SkRefCnt.h"
 
 class SkReadBuffer;
 class SkWriteBuffer;
 
 /** \class SkTextBlob
 
     SkTextBlob combines multiple text runs into an immutable, ref-counted structure.
 */
-class SK_API SkTextBlob : public SkRefCnt {
+class SK_API SkTextBlob final : public SkNVRefCnt<SkTextBlob> {
 public:
     /**
      *  Returns a conservative blob bounding box.
      */
     const SkRect& bounds() const { return fBounds; }
 
     /**
      *  Return a non-zero, unique value representing the text blob.
      */
     uint32_t uniqueID() const { return fUniqueID; }
@@ skipping 12 matching lines @@
      */
     static const SkTextBlob* CreateFromBuffer(SkReadBuffer&);
 
     enum GlyphPositioning {
         kDefault_Positioning      = 0, // Default glyph advances -- zero scalars per glyph.
         kHorizontal_Positioning   = 1, // Horizontal positioning -- one scalar per glyph.
         kFull_Positioning         = 2  // Point positioning -- two scalars per glyph.
     };
 
 private:
+    friend class SkNVRefCnt<SkTextBlob>;
     class RunRecord;
 
     SkTextBlob(int runCount, const SkRect& bounds);
 
-    virtual ~SkTextBlob();
+    ~SkTextBlob();
 
     // Memory for objects of this class is created with sk_malloc rather than operator new and must
     // be freed with sk_free.
     void operator delete(void* p) { sk_free(p); }
     void* operator new(size_t) {
         SkFAIL("All blobs are created by placement new.");
         return sk_malloc_throw(0);
     }
     void* operator new(size_t, void* p) { return p; }
 
@@ skipping 104 matching lines @@
 
     SkRect                 fBounds;
     int                    fRunCount;
     bool                   fDeferredBounds;
     size_t                 fLastRun; // index into fStorage
 
     RunBuffer              fCurrentRunBuffer;
 };
 
 #endif // SkTextBlob_DEFINED