diff -r 000000000000 -r 6474c204b198 layout/base/nsPresArena.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/layout/base/nsPresArena.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,136 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=2 sw=2 et tw=78:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+/* arena allocation for the frame tree and closely-related objects */
+
+#ifndef nsPresArena_h___
+#define nsPresArena_h___
+
+#include "mozilla/MemoryChecking.h" // Note: Do not remove this, needed for MOZ_HAVE_MEM_CHECKS below
+#include "mozilla/MemoryReporting.h"
+#include <stdint.h>
+#include "nscore.h"
+#include "nsQueryFrame.h"
+#include "nsTArray.h"
+#include "nsTHashtable.h"
+#include "plarena.h"
+
+struct nsArenaMemoryStats;
+
+class nsPresArena {
+public:
+  nsPresArena();
+  ~nsPresArena();
+
+  enum ObjectID {
+    nsLineBox_id = nsQueryFrame::NON_FRAME_MARKER,
+    nsRuleNode_id,
+    nsStyleContext_id,
+    nsFrameList_id,
+
+    /**
+     * The PresArena implementation uses this bit to distinguish objects
+     * allocated by size from objects allocated by type ID (that is, frames
+     * using AllocateByFrameID and other objects using AllocateByObjectID).
+     * It should not collide with any Object ID (above) or frame ID (in
+     * nsQueryFrame.h).  It is not 0x80000000 to avoid the question of
+     * whether enumeration constants are signed.
+     */
+    NON_OBJECT_MARKER = 0x40000000
+  };
+
+  /**
+   * Pool allocation with recycler lists indexed by object size, aSize.
+   */
+  NS_HIDDEN_(void*) AllocateBySize(size_t aSize)
+  {
+    return Allocate(uint32_t(aSize) | uint32_t(NON_OBJECT_MARKER), aSize);
+  }
+  NS_HIDDEN_(void) FreeBySize(size_t aSize, void* aPtr)
+  {
+    Free(uint32_t(aSize) | uint32_t(NON_OBJECT_MARKER), aPtr);
+  }
+
+  /**
+   * Pool allocation with recycler lists indexed by frame-type ID.
+   * Every aID must always be used with the same object size, aSize.
+   */
+  NS_HIDDEN_(void*) AllocateByFrameID(nsQueryFrame::FrameIID aID, size_t aSize)
+  {
+    return Allocate(aID, aSize);
+  }
+  NS_HIDDEN_(void) FreeByFrameID(nsQueryFrame::FrameIID aID, void* aPtr)
+  {
+    Free(aID, aPtr);
+  }
+
+  /**
+   * Pool allocation with recycler lists indexed by object-type ID (see above).
+   * Every aID must always be used with the same object size, aSize.
+   */
+  NS_HIDDEN_(void*) AllocateByObjectID(ObjectID aID, size_t aSize)
+  {
+    return Allocate(aID, aSize);
+  }
+  NS_HIDDEN_(void) FreeByObjectID(ObjectID aID, void* aPtr)
+  {
+    Free(aID, aPtr);
+  }
+
+  /**
+   * Increment aArenaStats with sizes of interesting objects allocated in this
+   * arena and its mOther field with the size of everything else.
+   */
+  void AddSizeOfExcludingThis(mozilla::MallocSizeOf aMallocSizeOf,
+                              nsArenaMemoryStats* aArenaStats);
+
+private:
+  NS_HIDDEN_(void*) Allocate(uint32_t aCode, size_t aSize);
+  NS_HIDDEN_(void) Free(uint32_t aCode, void* aPtr);
+
+  // All keys to this hash table fit in 32 bits (see below) so we do not
+  // bother actually hashing them.
+  class FreeList : public PLDHashEntryHdr
+  {
+  public:
+    typedef uint32_t KeyType;
+    nsTArray<void *> mEntries;
+    size_t mEntrySize;
+    size_t mEntriesEverAllocated;
+
+    typedef const void* KeyTypePointer;
+    KeyTypePointer mKey;
+
+    FreeList(KeyTypePointer aKey)
+    : mEntrySize(0), mEntriesEverAllocated(0), mKey(aKey) {}
+    // Default copy constructor and destructor are ok.
+
+    bool KeyEquals(KeyTypePointer const aKey) const
+    { return mKey == aKey; }
+
+    static KeyTypePointer KeyToPointer(KeyType aKey)
+    { return NS_INT32_TO_PTR(aKey); }
+
+    static PLDHashNumber HashKey(KeyTypePointer aKey)
+    { return NS_PTR_TO_INT32(aKey); }
+
+    enum { ALLOW_MEMMOVE = false };
+  };
+
+#if defined(MOZ_HAVE_MEM_CHECKS)
+  static PLDHashOperator UnpoisonFreeList(FreeList* aEntry, void*);
+#endif
+  static PLDHashOperator FreeListEnumerator(FreeList* aEntry, void* aData);
+  static size_t SizeOfFreeListEntryExcludingThis(FreeList* aEntry,
+                                                 mozilla::MallocSizeOf aMallocSizeOf,
+                                                 void*);
+
+  nsTHashtable<FreeList> mFreeLists;
+  PLArenaPool mPool;
+};
+
+#endif