--- a/ipc/glue/Makefile.in
+++ b/ipc/glue/Makefile.in
@@ -84,16 +84,17 @@ ENABLE_CXX_EXCEPTIONS = 1
 CPPSRCS += \
   AsyncChannel.cpp \
   BrowserProcessSubThread.cpp \
   GeckoChildProcessHost.cpp \
   MessagePump.cpp \
   ProcessChild.cpp \
   RPCChannel.cpp \
   ScopedXREEmbed.cpp \
+  SharedMemory.cpp \
   Shmem.cpp \
   StringUtil.cpp \
   SyncChannel.cpp \
   $(NULL)
 
 ifeq ($(OS_ARCH),WINNT)
 CPPSRCS += \
   SharedMemory_windows.cpp \

new file mode 100644
--- /dev/null
+++ b/ipc/glue/SharedMemory.cpp
@@ -0,0 +1,57 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: sw=2 ts=8 et :
+ */
+/* ***** BEGIN LICENSE BLOCK *****
+ * Version: MPL 1.1/GPL 2.0/LGPL 2.1
+ *
+ * The contents of this file are subject to the Mozilla Public License Version
+ * 1.1 (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at:
+ * http://www.mozilla.org/MPL/
+ *
+ * Software distributed under the License is distributed on an "AS IS" basis,
+ * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
+ * for the specific language governing rights and limitations under the
+ * License.
+ *
+ * The Original Code is Mozilla Code.
+ *
+ * The Initial Developer of the Original Code is
+ *   The Mozilla Foundation
+ * Portions created by the Initial Developer are Copyright (C) 2010
+ * the Initial Developer. All Rights Reserved.
+ *
+ * Contributor(s):
+ *   Chris Jones <jones.chris.g@gmail.com>
+ *
+ * Alternatively, the contents of this file may be used under the terms of
+ * either the GNU General Public License Version 2 or later (the "GPL"), or
+ * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
+ * in which case the provisions of the GPL or the LGPL are applicable instead
+ * of those above. If you wish to allow use of your version of this file only
+ * under the terms of either the GPL or the LGPL, and not to allow others to
+ * use your version of this file under the terms of the MPL, indicate your
+ * decision by deleting the provisions above and replace them with the notice
+ * and other provisions required by the GPL or the LGPL. If you do not delete
+ * the provisions above, a recipient may use your version of this file under
+ * the terms of any one of the MPL, the GPL or the LGPL.
+ *
+ * ***** END LICENSE BLOCK ***** */
+
+#include <math.h>
+
+#include "mozilla/ipc/SharedMemory.h"
+
+namespace mozilla {
+namespace ipc {
+
+/*static*/ size_t
+SharedMemory::PageAlignedSize(size_t aSize)
+{
+  size_t pageSize = SystemPageSize();
+  size_t nPagesNeeded = size_t(ceil(double(aSize) / double(pageSize)));
+  return pageSize * nPagesNeeded;
+}
+
+} // namespace ipc
+} // namespace mozilla

--- a/ipc/glue/SharedMemory.h
+++ b/ipc/glue/SharedMemory.h
@@ -98,15 +98,16 @@ public:
     // checks alignment etc.
     SystemProtect(aAddr, aSize, aRights);
   }
 
   NS_INLINE_DECL_REFCOUNTING(SharedMemory)
 
   static void SystemProtect(char* aAddr, size_t aSize, int aRights);
   static size_t SystemPageSize();
+  static size_t PageAlignedSize(size_t aSize);
 };
 
 } // namespace ipc
 } // namespace mozilla
 
 
 #endif // ifndef mozilla_ipc_SharedMemory_h

--- a/ipc/glue/Shmem.cpp
+++ b/ipc/glue/Shmem.cpp
@@ -33,18 +33,16 @@
  * use your version of this file under the terms of the MPL, indicate your
  * decision by deleting the provisions above and replace them with the notice
  * and other provisions required by the GPL or the LGPL. If you do not delete
  * the provisions above, a recipient may use your version of this file under
  * the terms of any one of the MPL, the GPL or the LGPL.
  *
  * ***** END LICENSE BLOCK ***** */
 
-#include <math.h>
-
 #include "Shmem.h"
 
 #include "ProtocolUtils.h"
 #include "SharedMemoryBasic.h"
 #include "SharedMemorySysV.h"
 
 #include "nsAutoPtr.h"
 
@@ -191,24 +189,16 @@ CreateSegment(size_t aNBytes, SharedMemo
 static void
 DestroySegment(SharedMemory* aSegment)
 {
   // the SharedMemory dtor closes and unmaps the actual OS shmem segment
   if (aSegment)
     aSegment->Release();
 }
 
-static size_t
-PageAlignedSize(size_t aSize)
-{
-  size_t pageSize = SharedMemory::SystemPageSize();
-  size_t nPagesNeeded = int(ceil(double(aSize) / double(pageSize)));
-  return pageSize * nPagesNeeded;
-}
-
 
 #if defined(DEBUG)
 
 static const char sMagic[] =
     "This little piggy went to market.\n"
     "This little piggy stayed at home.\n"
     "This little piggy has roast beef,\n"
     "This little piggy had none.\n"
@@ -396,17 +386,17 @@ Shmem::Alloc(IHadBetterBeIPDLCodeCalling
              bool aProtect)
 {
   NS_ASSERTION(aNBytes <= PR_UINT32_MAX, "Will truncate shmem segment size!");
   NS_ABORT_IF_FALSE(!aProtect || !aUnsafe, "protect => !unsafe");
 
   size_t pageSize = SharedMemory::SystemPageSize();
   SharedMemory* segment = nsnull;
   // |2*pageSize| is for the front and back sentinel
-  size_t segmentSize = PageAlignedSize(aNBytes + 2*pageSize);
+  size_t segmentSize = SharedMemory::PageAlignedSize(aNBytes + 2*pageSize);
 
   if (aType == SharedMemory::TYPE_BASIC)
     segment = CreateSegment(segmentSize, SharedMemoryBasic::NULLHandle());
 #ifdef MOZ_HAVE_SHAREDMEMORYSYSV
   else if (aType == SharedMemory::TYPE_SYSV)
     segment = CreateSegment(segmentSize, SharedMemorySysV::NULLHandle());
 #endif
   else
@@ -452,17 +442,17 @@ Shmem::OpenExisting(IHadBetterBeIPDLCode
   SharedMemory::SharedMemoryType type;
   size_t size;
   if (!ShmemCreated::ReadInfo(&aDescriptor, &iter, aId, &size, &type))
     return 0;
 
   SharedMemory* segment = 0;
   size_t pageSize = SharedMemory::SystemPageSize();
   // |2*pageSize| is for the front and back sentinels
-  size_t segmentSize = PageAlignedSize(size + 2*pageSize);
+  size_t segmentSize = SharedMemory::PageAlignedSize(size + 2*pageSize);
 
   if (SharedMemory::TYPE_BASIC == type) {
     SharedMemoryBasic::Handle handle;
     if (!ShmemCreated::ReadHandle(&aDescriptor, &iter, &handle))
       return 0;
 
     if (!SharedMemoryBasic::IsHandleValid(handle))
       NS_RUNTIMEABORT("trying to open invalid handle");
@@ -527,21 +517,21 @@ Shmem::Alloc(IHadBetterBeIPDLCodeCalling
              size_t aNBytes, 
              SharedMemoryType aType,
              bool /*unused*/,
              bool /*unused*/)
 {
   SharedMemory *segment = nsnull;
 
   if (aType == SharedMemory::TYPE_BASIC)
-    segment = CreateSegment(PageAlignedSize(aNBytes + sizeof(uint32)),
+    segment = CreateSegment(SharedMemory::PageAlignedSize(aNBytes + sizeof(uint32)),
                             SharedMemoryBasic::NULLHandle());
 #ifdef MOZ_HAVE_SHAREDMEMORYSYSV
   else if (aType == SharedMemory::TYPE_SYSV)
-    segment = CreateSegment(PageAlignedSize(aNBytes + sizeof(uint32)),
+    segment = CreateSegment(SharedMemory::PageAlignedSize(aNBytes + sizeof(uint32)),
                             SharedMemorySysV::NULLHandle());
 #endif
   else
     // Unhandled!!
     NS_ABORT();
 
   if (!segment)
     return 0;
@@ -563,17 +553,17 @@ Shmem::OpenExisting(IHadBetterBeIPDLCode
 
   SharedMemory::SharedMemoryType type;
   void* iter = 0;
   size_t size;
   if (!ShmemCreated::ReadInfo(&aDescriptor, &iter, aId, &size, &type))
     return 0;
 
   SharedMemory* segment = 0;
-  size_t segmentSize = PageAlignedSize(size + sizeof(size_t));
+  size_t segmentSize = SharedMemory::PageAlignedSize(size + sizeof(size_t));
 
   if (SharedMemory::TYPE_BASIC == type) {
     SharedMemoryBasic::Handle handle;
     if (!ShmemCreated::ReadHandle(&aDescriptor, &iter, &handle))
       return 0;
 
     if (!SharedMemoryBasic::IsHandleValid(handle))
       NS_RUNTIMEABORT("trying to open invalid handle");

--- a/widget/src/shared/nsShmImage.cpp
+++ b/widget/src/shared/nsShmImage.cpp
@@ -46,16 +46,18 @@
 #endif
 
 #include "nsShmImage.h"
 #include "gfxPlatform.h"
 #include "gfxImageSurface.h"
 
 #ifdef MOZ_HAVE_SHMIMAGE
 
+using namespace mozilla::ipc;
+
 // If XShm isn't available to our client, we'll try XShm once, fail,
 // set this to false and then never try again.
 static PRBool gShmAvailable = PR_TRUE;
 PRBool nsShmImage::UseShm()
 {
     return gfxPlatform::GetPlatform()->
         ScreenReferenceSurface()->GetType() == gfxASurface::SurfaceTypeImage
         && gShmAvailable;
@@ -71,17 +73,18 @@ nsShmImage::Create(const gfxIntSize& aSi
     shm->mImage = XShmCreateImage(dpy, aVisual, aDepth,
                                   ZPixmap, nsnull,
                                   &(shm->mInfo),
                                   aSize.width, aSize.height);
     if (!shm->mImage) {
         return nsnull;
     }
 
-    size_t size = shm->mImage->bytes_per_line * shm->mImage->height;
+    size_t size = SharedMemory::PageAlignedSize(
+        shm->mImage->bytes_per_line * shm->mImage->height);
     shm->mSegment = new SharedMemorySysV();
     if (!shm->mSegment->Create(size) || !shm->mSegment->Map(size)) {
         return nsnull;
     }
 
     shm->mInfo.shmid = shm->mSegment->GetHandle();
     shm->mInfo.shmaddr =
         shm->mImage->data = static_cast<char*>(shm->mSegment->memory());

--- a/widget/src/shared/nsShmImage.h
+++ b/widget/src/shared/nsShmImage.h
@@ -63,21 +63,21 @@
 #elif defined(MOZ_WIDGET_QT)
 #include "QX11Info"
 #define DISPLAY QX11Info().display
 #endif
 
 class QRect;
 class QWidget;
 
-using mozilla::ipc::SharedMemorySysV;
-
 class nsShmImage {
     NS_INLINE_DECL_REFCOUNTING(nsShmImage)
 
+    typedef mozilla::ipc::SharedMemorySysV SharedMemorySysV;
+
 public:
     typedef gfxASurface::gfxImageFormat Format;
 
     static PRBool UseShm();
     static already_AddRefed<nsShmImage>
         Create(const gfxIntSize& aSize, Visual* aVisual, unsigned int aDepth);
     static already_AddRefed<gfxASurface>
         EnsureShmImage(const gfxIntSize& aSize, Visual* aVisual, unsigned int aDepth,