Add SkNVRefCnt, prune down SkPicture's size

include/core/SkRefCnt.h

Index: include/core/SkRefCnt.h
diff --git a/include/core/SkRefCnt.h b/include/core/SkRefCnt.h
index 4da2fbbc936266662a4510b64a8ce3a9de921972..fd49cbea30b85e8b66d6607589e2eac7de325d9e 100644
--- a/include/core/SkRefCnt.h
+++ b/include/core/SkRefCnt.h
@@ -247,4 +247,21 @@ public:
 };
 #define SkAutoUnref(...) SK_REQUIRE_LOCAL_VAR(SkAutoUnref)
 

[tomhudson, 2014/11/19 18:59:06]

Can we put something like a short version of the CL description here as a class
header comment? Since there's an abbreviation in the class name, the purpose of
the class isn't clear, and even spelling out the abbreviation leaves it
inobvious.

[mtklein, 2014/11/19 19:19:14]

Done.

+template <typename Derived>
+class SkNVRefCnt : SkNoncopyable {
+public:
+    SkNVRefCnt() : fRefCnt(1) {}
+
+    // Implementation is pretty much the same as SkRefCntBase. All required barriers are the same:
+    //   - unique() needs acquire when it returns true, and no barrier if it returns false;
+    //   - ref() doesn't need any barrier;
+    //   - unref() needs a release barrier, and an acquire if it's going to call delete.
+
+    bool unique() const { return 1 == sk_acquire_load(&fRefCnt); }
+    void    ref() const { sk_atomic_inc(&fRefCnt); }
+    void  unref() const { if (1 == sk_atomic_dec(&fRefCnt)) { SkDELETE((const Derived*)this); } }
+private:
+    mutable int32_t fRefCnt;
+};
+
 #endif