Bug 1618868 Part 2: Make counts and states in CanvasEventRingBuffer footers SequentiallyConsistent. r=jrmuizel

This fixes an issue with the AboutToWait check. It is possible that this could
be done without this, but while there might be a very slight performance hit, it
seems to be smaller than the general noise in the tests.

Depends on D70335

Differential Revision: https://phabricator.services.mozilla.com/D70336

--HG--
extra : moz-landing-system : lando

gfx/layers/CanvasDrawEventRecorder.h

@@ -182,16 +182,16 @@ class CanvasEventRingBuffer final : public gfx::EventRingBuffer {
   };
 
   struct ReadFooter {
-    Atomic<uint32_t, ReleaseAcquire> count;
-    Atomic<uint32_t, ReleaseAcquire> returnCount;
-    Atomic<State, ReleaseAcquire> state;
+    Atomic<uint32_t> count;
+    Atomic<uint32_t> returnCount;
+    Atomic<State> state;
   };
 
   struct WriteFooter {
-    Atomic<uint32_t, ReleaseAcquire> count;
-    Atomic<uint32_t, ReleaseAcquire> returnCount;
-    Atomic<uint32_t, ReleaseAcquire> requiredDifference;
-    Atomic<State, ReleaseAcquire> state;
+    Atomic<uint32_t> count;
+    Atomic<uint32_t> returnCount;
+    Atomic<uint32_t> requiredDifference;
+    Atomic<State> state;
   };
 
   CanvasEventRingBuffer(const CanvasEventRingBuffer&) = delete;