Add some support for promptly purging pages.

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

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef PageMemory_h
 #define PageMemory_h
 
 #include "platform/heap/HeapPage.h"
 #include "platform/wtf/Allocator.h"
 #include "platform/wtf/Assertions.h"
@@ skipping 16 matching lines @@
   bool Contains(Address addr) const {
     return base_ <= addr && addr < (base_ + size_);
   }
 
   bool Contains(const MemoryRegion& other) const {
     return Contains(other.base_) && Contains(other.base_ + other.size_ - 1);
   }
 
   void Release();
   WARN_UNUSED_RESULT bool Commit();
-  void Decommit();
+  void Decommit(DecommitMemoryTiming);
 
   Address Base() const { return base_; }
   size_t size() const { return size_; }
 
  private:
   Address base_;
   size_t size_;
 };
 
 // A PageMemoryRegion represents a chunk of reserved virtual address
@@ skipping 125 matching lines @@
     // when allocating new pages, but crbug.com/649485 suggests that
     // we do get out of sync somehow.
     //
     // TODO(sof): consider removing check once bug has been diagnosed
     // and addressed.
     CHECK(!ThreadState::Current()->IsAddressInHeapDoesNotContainCache(
         WritableStart()));
     return writable_.Commit();
   }
 
-  void Decommit() {
+  void Decommit(DecommitMemoryTiming decommit_hint) {
     reserved_->MarkPageUnused(WritableStart());
-    writable_.Decommit();
+    writable_.Decommit(decommit_hint);
   }
 
   void MarkUnused() { reserved_->MarkPageUnused(WritableStart()); }
 
   PageMemoryRegion* Region() { return reserved_; }
 
   Address WritableStart() { return writable_.Base(); }
 
   static PageMemory* SetupPageMemoryInRegion(PageMemoryRegion*,
                                              size_t page_offset,
@@ skipping 12 matching lines @@
  private:
   PageMemory(PageMemoryRegion* reserved, const MemoryRegion& writable);
 
   PageMemoryRegion* reserved_;
   MemoryRegion writable_;
 };
 
 }  // namespace blink
 
 #endif