Modernize and trim down SkOnce.

The API and implementation are very much simplified.
You may not want to bother reading the diff.

As is our trend, SkOnce now uses <atomic> directly.

Member initialization means we don't need SK_DECLARE_STATIC_ONCE.
SkSpinlock already works this same way.

All uses of the old API taking an external bool* and Lock* were pessimal,
so I have not carried this sort of API forward.  It's simpler, faster,
and more space-efficient to always use this single SkOnce class interface.

SkOnce weighs 2 bytes: a done bool and an SkSpinlock, also a bool internally.
This API refactoring opens up the opportunity to fuse those into a single
three-state byte if we'd like.

No public API changes.
TBR=reed@google.com

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1894893002

Review URL: https://codereview.chromium.org/1894893002

1 files changed, 2 insertions, 2 deletions

diff --git a/tools/gpu/gl/command_buffer/GLTestContext_command_buffer.cpp b/tools/gpu/gl/command_buffer/GLTestContext_command_buffer.cpp
index af0abc5853..850adaaf25 100644
--- a/tools/gpu/gl/command_buffer/GLTestContext_command_buffer.cpp
+++ b/tools/gpu/gl/command_buffer/GLTestContext_command_buffer.cpp
@@ -127,9 +127,9 @@ static GrGLFuncPtr command_buffer_get_gl_proc(void* ctx, const char name[]) {
     return gfGetProcAddress(name);
 }
 
-SK_DECLARE_STATIC_ONCE(loadCommandBufferOnce);
 static void load_command_buffer_once() {
-    SkOnce(&loadCommandBufferOnce, load_command_buffer_functions);
+    static SkOnce once;
+    once(load_command_buffer_functions);
 }
 
 static const GrGLInterface* create_command_buffer_interface() {