Add GrNonAtomicRef

src/gpu/GrNonAtomicRef.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 GrNonAtomicRef_DEFINED
+#define GrNonAtomicRef_DEFINED
+
+#include "SkRefCnt.h"
+#include "SkTArray.h"
+
+/**
+ * A simple non-atomic ref used in the GrBackend when we don't want to pay for the overhead of a
+ * threadsafe ref counted object
+ */
+class GrNonAtomicRef : public SkNoncopyable {
+public:
+    GrNonAtomicRef() : fRefCnt(1) {}
+    virtual ~GrNonAtomicRef() {
+        // fRefCnt can be one when a subclass is created statically
+        SkASSERT((0 == fRefCnt || 1 == fRefCnt));
+        // Set to invalid values.
+        SkDEBUGCODE(fRefCnt = -10;)
+    }
+
+    void ref() const {
+        // Once the ref cnt reaches zero it should never be ref'ed again.
+        SkASSERT(fRefCnt > 0);
+        ++fRefCnt;
+    }
+
+    void unref() const {
+        SkASSERT(fRefCnt > 0);
+        --fRefCnt;
+        if (0 == fRefCnt) {
+            SkDELETE(this);
+            return;
+        }
+    }
+
+private:
+    mutable int32_t fRefCnt;
+
+    typedef SkNoncopyable INHERITED;
+};
+
+#endif