Add some support for promptly purging pages.

third_party/WebKit/Source/platform/heap/PageMemory.cpp

Index: third_party/WebKit/Source/platform/heap/PageMemory.cpp
diff --git a/third_party/WebKit/Source/platform/heap/PageMemory.cpp b/third_party/WebKit/Source/platform/heap/PageMemory.cpp
index 96c5e2acc6342e75d5cc17c774466a086759a2d4..5abcd5d16c18b957983fb53576e72d9b9fd35c5a 100644
--- a/third_party/WebKit/Source/platform/heap/PageMemory.cpp
+++ b/third_party/WebKit/Source/platform/heap/PageMemory.cpp
@@ -20,9 +20,10 @@ bool MemoryRegion::Commit() {
   return WTF::SetSystemPagesAccessible(base_, size_);
 }
 
-void MemoryRegion::Decommit() {
+void MemoryRegion::Decommit(DecommitMemoryTiming decommit_hint) {
   ASAN_UNPOISON_MEMORY_REGION(base_, size_);
-  WTF::DecommitSystemPages(base_, size_);
+  WTF::DecommitSystemPages(
+      base_, size_, decommit_hint == DecommitMemoryTiming::DecommitPromptly);
   WTF::SetSystemPagesInaccessible(base_, size_);
 }