Reland of SkOncePtr -> SkOnce (patchset #1 id:1 of https://codereview.chromium.org/1945293004/ )

Reason for revert:
previous revert unneeded (I think)

Original issue's description:
> Revert of SkOncePtr -> SkOnce (patchset #4 id:60001 of https://codereview.chromium.org/1953533002/ )
>
> Reason for revert:
> broken the Mac and Linux builders, e.g.:
>
> https://build.chromium.org/p/chromium/builders/Mac/builds/15151
> https://build.chromium.org/p/chromium/builders/Linux%20x64/builds/19052
>
> Original issue's description:
> > SkOncePtr -> SkOnce
> >
> > It's always nice to kill off a synchronization primitive.
> > And while less terse, I think this new code reads more clearly.
> >
> > ... and, SkOncePtr's tests were the only thing now using sk_num_cores()
> > outside of SkTaskGroup, so I've hidden it as static inside SkTaskGroup.cpp.
> >
> > BUG=skia:
> > GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1953533002
> > CQ_EXTRA_TRYBOTS=client.skia:Test-Ubuntu-GCC-GCE-CPU-AVX2-x86_64-Release-SKNX_NO_SIMD-Trybot
> >
> > Committed: https://skia.googlesource.com/skia/+/9bd3fc7fa9bb7cad050bd619aa93d4c48ebb5c02
>
> TBR=herb@google.com,mtklein@chromium.org
> # Skipping CQ checks because original CL landed less than 1 days ago.
> NOPRESUBMIT=true
> NOTREECHECKS=true
> NOTRY=true
> BUG=skia:
>
> Committed: https://skia.googlesource.com/skia/+/7eb33da7eede34c050b865dbb1b60c3dcea7191b

TBR=herb@google.com,mtklein@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=skia:

Review-Url: https://codereview.chromium.org/1949313003

1 files changed, 0 insertions, 65 deletions

diff --git a/include/private/SkOncePtr.h b/include/private/SkOncePtr.h
deleted file mode 100644
index 921c6a6534..0000000000
--- a/include/private/SkOncePtr.h
+++ /dev/null
@@ -1,65 +0,0 @@
-/*
- * 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 SkOncePtr_DEFINED
-#define SkOncePtr_DEFINED
-
-#include "../private/SkAtomics.h"
-#include <memory>
-
-// Use this to create a global static pointer that's intialized exactly once when you call get().
-#define SK_DECLARE_STATIC_ONCE_PTR(type, name) namespace {} static SkBaseOncePtr<type> name;
-
-template <typename T>
-class SkBaseOncePtr {
-public:
-    template <typename F>
-    T* get(const F& f) const {
-        uintptr_t state = sk_atomic_load(&fState, sk_memory_order_acquire);
-        if (state < 2) {
-            if (state == 0) {
-                // It looks like no one has tried to create our pointer yet.
-                // We try to claim that task by atomically swapping our state from '0' to '1'.
-                // See SkOnce.h for why we use an acquire memory order here rather than relaxed.
-                if (sk_atomic_compare_exchange(
-                    &fState, &state, (uintptr_t)1, sk_memory_order_acquire, sk_memory_order_acquire)) {
-                    // We've claimed it.  Create our pointer and store it into fState.
-                    state = (uintptr_t)f();
-                    SkASSERT(state > 1);
-                    sk_atomic_store(&fState, state, sk_memory_order_release);
-                } else {
-                    // Someone else claimed it.
-                    // We fall through to the spin loop just below to wait for them to finish.
-                }
-            }
-
-            while (state == 1) {
-                // State '1' is our busy-but-not-done state.
-                // Some other thread has claimed the job of creating our pointer.
-                // We just need to wait for it to finish.
-                state = sk_atomic_load(&fState, sk_memory_order_acquire);
-            }
-
-            // We shouldn't be able to get here without having created our pointer.
-            SkASSERT(state > 1);
-        }
-        return (T*)state;
-    }
-
-    operator T*() const {
-        auto state = sk_atomic_load(&fState, sk_memory_order_acquire);
-        return state < 2 ? nullptr : (T*)state;
-        // TODO: If state == 1 spin until it's not?
-    }
-
-    // fState == 0 --> we have not created our ptr yet
-    // fState == 1 --> someone is in the middle of creating our ptr
-    // else        --> (T*)fState is our ptr
-    mutable uintptr_t fState;
-};
-
-#endif//SkOncePtr_DEFINED