make SkRecord normally SkRefCnt'd

SkRecord used SkNVRefCnt to avoid adding a vptr.

SkMiniPicture covers the really small allocations,
so there's really no reason to fret over an extra pointer here.

BUG=skia:6484

Change-Id: Ifa43be8eb352b2d59851c75e6b4f164bb38b5ef6
Reviewed-on: https://skia-review.googlesource.com/13139
Reviewed-by: Herb Derby <herb@google.com>
Commit-Queue: Mike Klein <mtklein@chromium.org>

src/core/SkRecord.h

@@ -25,7 +25,7 @@
 // only with SkRecords::* structs defined in SkRecords.h.  Your compiler will helpfully yell if you
 // get this wrong.
 
-class SkRecord : public SkNVRefCnt<SkRecord> {
+class SkRecord : public SkRefCnt {
     enum {
         // TODO: tune these two constants.
         kInlineRecords      = 4, // Ideally our lower limit on recorded ops per picture.