Port SkLazyFnPtr users to SkOncePtr.

src/core/SkLazyFnPtr.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 SkLazyFnPtr_DEFINED
-#define SkLazyFnPtr_DEFINED
-
-/** Declare a lazily-chosen static function pointer of type F.
- *
- *  Example usage:
- *
- *  typedef int (*FooImpl)(int, int);
- *
- *  static FooImpl choose_foo() { return ... };
- *
- *  int Foo(int a, int b) {
- *     SK_DECLARE_STATIC_LAZY_FN_PTR(FooImpl, foo, choose_foo);
- *     return foo.get()(a, b);
- *  }
- *
- *  You can think of SK_DECLARE_STATIC_LAZY_FN_PTR as a cheaper specialization of SkOnce.
- *  There is no mutex, and in the fast path, no memory barriers are issued.
- *
- *  This must be used in a global or function scope, not as a class member.
- */
-#define SK_DECLARE_STATIC_LAZY_FN_PTR(F, name, Choose) static Private::SkLazyFnPtr<F, Choose> name
-
-
-// Everything below here is private implementation details.  Don't touch, don't even look.
-
-#include "SkAtomics.h"
-
-namespace Private {
-
-// This has no constructor and must be zero-initialized (the macro above does this).
-template <typename F, F (*Choose)()>
-class SkLazyFnPtr {
-public:
-    F get() {
-        // First, try reading to see if it's already set.
-        F fn = (F)sk_atomic_load(&fPtr, sk_memory_order_relaxed);
-        if (fn != nullptr) {
-            return fn;
-        }
-
-        // We think it's not already set.
-        fn = Choose();
-
-        // No particular memory barriers needed; we're not guarding anything but the pointer itself.
-        F prev = (F)sk_atomic_cas(&fPtr, nullptr, (void*)fn);
-
-        // If prev != nullptr, someone snuck in and set fPtr concurrently.
-        // If prev == nullptr, we did write fn to fPtr.
-        return prev != nullptr ? prev : fn;
-    }
-
-private:
-    void* fPtr;
-};
-
-}  // namespace Private
-
-#endif//SkLazyFnPtr_DEFINED