Replace RenderArena with PartitionAlloc.

Source/wtf/PartitionAlloc.cpp

Index: Source/wtf/PartitionAlloc.cpp
diff --git a/Source/wtf/PartitionAlloc.cpp b/Source/wtf/PartitionAlloc.cpp
index 47c06083b6b6e6cdfedba4bf6da6b415b2e64299..e2d122ef221edb23ec43b2d949eaf16940cb04f4 100644
--- a/Source/wtf/PartitionAlloc.cpp
+++ b/Source/wtf/PartitionAlloc.cpp
@@ -317,6 +317,23 @@ void partitionFreeSlowPath(PartitionPageHeader* page)
     }
 }
 
+size_t partitionAllocGetUsedPagesSize(const PartitionRoot& root)
+{
+    size_t total = 0;
+    size_t i;
+    for (i = 0; i < kNumBuckets; ++i) {
+        const PartitionBucket& bucket = root.buckets[i];
+        total += bucket.numFullPages * kPartitionPageSize;
+        const PartitionPageHeader* page = bucket.currPage;
+        do {
+            if (page != &bucket.root->seedPage)
+                total += kPartitionPageSize;
+            page = page->next;
+        } while (page != bucket.currPage);
+    }
+    return total;
+}
+
 #ifndef NDEBUG
 
 void partitionDumpStats(const PartitionRoot& root)