PartitionAlloc: Count direct mapped pages as committed

Source/wtf/PartitionAlloc.h

Index: Source/wtf/PartitionAlloc.h
diff --git a/Source/wtf/PartitionAlloc.h b/Source/wtf/PartitionAlloc.h
index 2ede593436dddabd4d30a2fb430c89a03a514479..6bc49146f1c0a42b412a1aa98bea2f1c6fbaf516 100644
--- a/Source/wtf/PartitionAlloc.h
+++ b/Source/wtf/PartitionAlloc.h
@@ -115,10 +115,10 @@
 
 namespace WTF {
 
-// Maximum size of a partition's mappings. 2046MB. Note that the total amount of
-// bytes allocatable at the API will be smaller. This is because things like
-// guard pages, metadata, page headers and wasted space come out of the total.
-// The 2GB is not necessarily contiguous in virtual address space.
+// Maximum size of a partition's committed memory. 2046MB. Note that the total
+// amount of bytes allocatable at the API will be slightly smaller. This is
+// because things like wasted space come out of the total. The 2GB is not
+// necessarily contiguous in virtual address space.
 static const size_t kMaxPartitionSize = 2046u * 1024u * 1024u;
 
 // Allocation granularity of sizeof(void*) bytes.