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, 10 insertions, 8 deletions

diff --git a/src/core/SkPathRef.cpp b/src/core/SkPathRef.cpp
index b18055136f..2fc2de935c 100644
--- a/src/core/SkPathRef.cpp
+++ b/src/core/SkPathRef.cpp
@@ -6,7 +6,7 @@
  */
 
 #include "SkBuffer.h"
-#include "SkOncePtr.h"
+#include "SkOnce.h"
 #include "SkPath.h"
 #include "SkPathRef.h"
 #include <limits>
@@ -45,13 +45,15 @@ SkPathRef::~SkPathRef() {
     SkDEBUGCODE(fEditorsAttached = 0x7777777;)
 }
 
-SK_DECLARE_STATIC_ONCE_PTR(SkPathRef, empty);
+static SkPathRef* gEmpty = nullptr;
+
 SkPathRef* SkPathRef::CreateEmpty() {
-    return SkRef(empty.get([]{
-        SkPathRef* pr = new SkPathRef;
-        pr->computeBounds();   // Avoids races later to be the first to do this.
-        return pr;
-    }));
+    static SkOnce once;
+    once([]{
+        gEmpty = new SkPathRef;
+        gEmpty->computeBounds();   // Avoids races later to be the first to do this.
+    });
+    return SkRef(gEmpty);
 }
 
 void SkPathRef::CreateTransformedCopy(SkAutoTUnref<SkPathRef>* dst,
@@ -469,7 +471,7 @@ uint32_t SkPathRef::genID() const {
 }
 
 void SkPathRef::addGenIDChangeListener(GenIDChangeListener* listener) {
-    if (nullptr == listener || this == (SkPathRef*)empty) {
+    if (nullptr == listener || this == gEmpty) {
         delete listener;
         return;
     }