Add some support for promptly purging pages.

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

Index: third_party/WebKit/Source/platform/heap/PageMemory.h
diff --git a/third_party/WebKit/Source/platform/heap/PageMemory.h b/third_party/WebKit/Source/platform/heap/PageMemory.h
index c985915197bef7132d931f28814d031b878885c7..a0bf2c1582a697d57056d6304bbd14059e001d98 100644
--- a/third_party/WebKit/Source/platform/heap/PageMemory.h
+++ b/third_party/WebKit/Source/platform/heap/PageMemory.h
@@ -34,7 +34,7 @@ class MemoryRegion {
 
   void Release();
   WARN_UNUSED_RESULT bool Commit();
-  void Decommit();
+  void Decommit(DecommitMemoryTiming);
 
   Address Base() const { return base_; }
   size_t size() const { return size_; }
@@ -180,9 +180,9 @@ class PageMemory {
     return writable_.Commit();
   }
 
-  void Decommit() {
+  void Decommit(DecommitMemoryTiming decommit_hint) {
     reserved_->MarkPageUnused(WritableStart());
-    writable_.Decommit();
+    writable_.Decommit(decommit_hint);
   }
 
   void MarkUnused() { reserved_->MarkPageUnused(WritableStart()); }