Expose ReleaseFreeMemory to free up memory on memory pressure or idle cleanup.

Source/wtf/PartitionAlloc.cpp

Index: Source/wtf/PartitionAlloc.cpp
diff --git a/Source/wtf/PartitionAlloc.cpp b/Source/wtf/PartitionAlloc.cpp
index d6fc5a6cdf2ebc3ca117b5909026b9ac4a315369..b714574e7f66025ba424bdf759b6b3c5da93e8ce 100644
--- a/Source/wtf/PartitionAlloc.cpp
+++ b/Source/wtf/PartitionAlloc.cpp
@@ -863,7 +863,7 @@ static ALWAYS_INLINE void partitionRegisterEmptyPage(PartitionPage* page)
     root->globalEmptyPageRingIndex = currentIndex;
 }
 
-void partitionPurgeMemory(PartitionRootBase* root)
+static void partitionDecommitFreePages(PartitionRootBase* root)
 {
     for (size_t i = 0; i < kMaxFreeableSpans; ++i) {
         PartitionPage* page = root->globalEmptyPageRing[i];
@@ -873,6 +873,18 @@ void partitionPurgeMemory(PartitionRootBase* root)
     }
 }
 
+void partitionPurgeMemory(PartitionRoot* root)
+{
+    partitionDecommitFreePages(root);
+}
+
+void partitionPurgeMemoryGeneric(PartitionRootGeneric* root)
+{
+    spinLockLock(&root->lock);
+    partitionDecommitFreePages(root);
+    spinLockUnlock(&root->lock);
+}
+
 void partitionFreeSlowPath(PartitionPage* page)
 {
     PartitionBucket* bucket = page->bucket;