[PartitionAlloc] Enable SpinningFutex in regular builds.

This was enabled only when DCHECK_IS_ON() to assess stability. Enable it
for regular builds as well to assess performance.

Bug: 1125999, 1061437
Change-Id: Ia38c81c95ed0e6ba3fab1754cb4809a08f1fea01
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2421651Reviewed-by: Kentaro Hara <haraken@chromium.org>
Commit-Queue: Benoit L <lizeb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#808942}

base/allocator/partition_allocator/partition_lock.h

@@ -142,8 +142,7 @@ class LOCKABLE MaybeSpinLock<true> {
   }
 
  private:
-  // DCHECK_IS_ON() for now to check stability before performance.
-#if DCHECK_IS_ON() && (defined(OS_LINUX) || defined(OS_ANDROID))
+#if defined(OS_LINUX) || defined(OS_ANDROID)
   base::NoDestructor<SpinningFutex> lock_;
 #else
   // base::Lock is slower on the fast path than SpinLock, hence we still use it