--- a/gfx/Makefile.in
+++ b/gfx/Makefile.in
@@ -43,17 +43,17 @@ VPATH		= @srcdir@
 include $(DEPTH)/config/autoconf.mk
 
 MODULE		= gfx
 
 ifdef MOZ_TREE_CAIRO
 DIRS		= cairo
 endif
 
-DIRS		+= thebes public idl src qcms
+DIRS		+= thebes public idl src qcms layers
 
 ifdef MOZ_IPC
 DIRS		+= ipc
 endif
 
 ifdef ENABLE_TESTS
 ifndef MOZ_ENABLE_LIBXUL
 TOOL_DIRS	+= tests

new file mode 100644
--- /dev/null
+++ b/gfx/layers/Layers.h
@@ -0,0 +1,384 @@
+/* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+ * ***** 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 Corporation code.
+ *
+ * The Initial Developer of the Original Code is Mozilla Foundation.
+ * Portions created by the Initial Developer are Copyright (C) 2009
+ * the Initial Developer. All Rights Reserved.
+ *
+ * Contributor(s):
+ *   Robert O'Callahan <robert@ocallahan.org>
+ *
+ * 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 ***** */
+
+#ifndef GFX_LAYERS_H
+#define GFX_LAYERS_H
+
+#include "gfxTypes.h"
+#include "nsRegion.h"
+#include "nsPoint.h"
+#include "nsRect.h"
+
+class gfxContext;
+class nsPaintEvent;
+
+namespace mozilla {
+namespace layers {
+
+class Layer;
+class ThebesLayer;
+class ContainerLayer;
+
+/*
+ * Motivation: For truly smooth animation and video playback, we need to
+ * be able to compose frames and render them on a dedicated thread (i.e.
+ * off the main thread where DOM manipulation, script execution and layout
+ * induce difficult-to-bound latency). This requires Gecko to construct
+ * some kind of persistent scene structure (graph or tree) that can be
+ * safely transmitted across threads. We have other scenarios (e.g. mobile 
+ * browsing) where retaining some rendered data between paints is desired
+ * for performance, so again we need a retained scene structure.
+ * 
+ * Our retained scene structure is a layer tree. Each layer represents
+ * content which can be composited onto a destination surface; the root
+ * layer is usually composited into a window, and non-root layers are
+ * composited into their parent layers. Layers have attributes (e.g.
+ * opacity and clipping) that influence their compositing.
+ * 
+ * We want to support a variety of layer implementations, including
+ * a simple "immediate mode" implementation that doesn't retain any
+ * rendered data between paints (i.e. uses cairo in just the way that
+ * Gecko used it before layers were introduced). But we also don't want
+ * to have bifurcated "layers"/"non-layers" rendering paths in Gecko.
+ * Therefore the layers API is carefully designed to permit maximally
+ * efficient implementation in an "immediate mode" style. See the
+ * BasicLayerManager for such an implementation.
+ */
+
+/**
+ * A LayerManager controls a tree of layers. All layers in the tree
+ * must use the same LayerManager.
+ * 
+ * All modifications to a layer tree must happen inside a transaction.
+ * Only the state of the layer tree at the end of a transaction is
+ * rendered. Transactions cannot be nested
+ * 
+ * Each transaction has two phases:
+ * 1) Construction: layers are created, inserted, removed and have
+ * properties set on them in this phase.
+ * BeginTransaction and BeginTransactionWithTarget start a transaction in
+ * the Construction phase. When the client has finished constructing the layer
+ * tree, it should call EndConstruction() to enter the drawing phase.
+ * 2) Drawing: ThebesLayers are rendered into in this phase, in tree
+ * order. When the client has finished drawing into the ThebesLayers, it should
+ * call EndTransaction to complete the transaction.
+ * 
+ * All layer API calls happen on the main thread.
+ * 
+ * Layers are refcounted. The layer manager holds a reference to the
+ * root layer, and each container layer holds a reference to its children.
+ */
+class THEBES_API LayerManager {
+  THEBES_INLINE_DECL_REFCOUNTING(LayerManager)  
+
+public:
+  virtual ~LayerManager() {}
+
+  /**
+   * Start a new transaction. Nested transactions are not allowed so
+   * there must be no transaction currently in progress.
+   * This transaction will update the state of the window from which
+   * this LayerManager was obtained.
+   */
+  virtual void BeginTransaction() = 0;
+  /**
+   * Start a new transaction. Nested transactions are not allowed so
+   * there must be no transaction currently in progress. 
+   * This transaction will render the contents of the layer tree to
+   * the given target context. The rendering will be complete when
+   * EndTransaction returns.
+   */
+  virtual void BeginTransactionWithTarget(gfxContext* aTarget) = 0;
+  /**
+   * Finish the construction phase of the transaction and enter the
+   * drawing phase.
+   */
+  virtual void EndConstruction() = 0;
+  /**
+   * Complete the transaction.
+   */
+  virtual void EndTransaction() = 0;
+
+  /**
+   * CONSTRUCTION PHASE ONLY
+   * Set the root layer.
+   */
+  virtual void SetRoot(Layer* aLayer) = 0;
+
+  /**
+   * CONSTRUCTION PHASE ONLY
+   * Create a ThebesLayer for this manager's layer tree.
+   */
+  virtual already_AddRefed<ThebesLayer> CreateThebesLayer() = 0;
+  /**
+   * CONSTRUCTION PHASE ONLY
+   * Create a ContainerLayer for this manager's layer tree.
+   */
+  virtual already_AddRefed<ContainerLayer> CreateContainerLayer() = 0;
+};
+
+/**
+ * A Layer represents anything that can be rendered onto a destination
+ * surface.
+ */
+class THEBES_API Layer {
+  THEBES_INLINE_DECL_REFCOUNTING(Layer)  
+
+public:
+  virtual ~Layer() {}
+
+  /**
+   * Returns the LayoutManager this Layer belongs to. Cannot be null.
+   */
+  LayerManager* Manager() { return mManager; }
+
+  /**
+   * CONSTRUCTION PHASE ONLY
+   * If this is called with aOpaque set to true, the caller is promising
+   * that by the end of this transaction the entire visible region
+   * (as specified by SetVisibleRegion) will be filled with opaque
+   * content. This enables some internal quality and performance
+   * optimizations.
+   */
+  void SetIsOpaqueContent(PRBool aOpaque) { mIsOpaqueContent = aOpaque; }
+  /**
+   * CONSTRUCTION PHASE ONLY
+   * Tell this layer which region will be visible. It is the responsibility
+   * of the caller to ensure that content outside this region does not
+   * contribute to the final visible window. This can be an
+   * overapproximation to the true visible region.
+   */
+  virtual void SetVisibleRegion(const nsIntRegion& aRegion) {}
+
+  /**
+   * CONSTRUCTION PHASE ONLY
+   * Set the opacity which will be applied to this layer as it
+   * is composited to the destination.
+   */
+  void SetOpacity(float aOpacity) { mOpacity = aOpacity; }
+
+  /**
+   * CONSTRUCTION PHASE ONLY
+   * Set a clip rect which will be applied to this layer as it is
+   * composited to the destination. The coordinates are relative to
+   * the parent layer (i.e. the contents of this layer
+   * are transformed before this clip rect is applied).
+   * For the root layer, the coordinates are relative to the widget,
+   * in device pixels.
+   * If aRect is null no clipping will be performed. 
+   */
+  void SetClipRect(const nsIntRect* aRect)
+  {
+    mUseClipRect = aRect != nsnull;
+    if (aRect) {
+      mClipRect = *aRect;
+    }
+  }
+  /**
+   * CONSTRUCTION PHASE ONLY
+   * Set a clip rect which will be applied to this layer as it is
+   * composited to the destination. The coordinates are relative to
+   * the parent layer (i.e. the contents of this layer
+   * are transformed before this clip rect is applied).
+   * For the root layer, the coordinates are relative to the widget,
+   * in device pixels.
+   * The provided rect is intersected with any existing clip rect.
+   */
+  void IntersectClipRect(const nsIntRect& aRect)
+  {
+    if (mUseClipRect) {
+      mClipRect.IntersectRect(mClipRect, aRect);
+    } else {
+      mUseClipRect = PR_TRUE;
+      mClipRect = aRect;
+    }
+  }
+
+  // These getters can be used anytime.
+  float GetOpacity() { return mOpacity; }
+  const nsIntRect* GetClipRect() { return mUseClipRect ? &mClipRect : nsnull; }
+  PRBool IsOpaqueContent() { return mIsOpaqueContent; }
+  ContainerLayer* GetParent() { return mParent; }
+  Layer* GetNextSibling() { return mNextSibling; }
+  Layer* GetPrevSibling() { return mPrevSibling; }
+  virtual Layer* GetFirstChild() { return nsnull; }
+
+  /**
+   * Only the implementation should call this. This is per-implementation
+   * private data. Normally, all layers with a given layer manager
+   * use the same type of ImplData.
+   */
+  void* ImplData() { return mImplData; }
+
+  /**
+   * Only the implementation should use these methods.
+   */
+  void SetParent(ContainerLayer* aParent) { mParent = aParent; }
+  void SetNextSibling(Layer* aSibling) { mNextSibling = aSibling; }
+  void SetPrevSibling(Layer* aSibling) { mPrevSibling = aSibling; }
+
+protected:
+  Layer(LayerManager* aManager, void* aImplData) :
+    mManager(aManager),
+    mParent(nsnull),
+    mNextSibling(nsnull),
+    mPrevSibling(nsnull),
+    mImplData(aImplData),
+    mOpacity(1.0),
+    mUseClipRect(PR_FALSE),
+    mIsOpaqueContent(PR_FALSE)
+    {}
+
+  LayerManager* mManager;
+  ContainerLayer* mParent;
+  Layer* mNextSibling;
+  Layer* mPrevSibling;
+  void* mImplData;
+  float mOpacity;
+  nsIntRect mClipRect;
+  PRPackedBool mUseClipRect;
+  PRPackedBool mIsOpaqueContent;
+};
+
+/**
+ * A Layer which we can draw into using Thebes. It is a conceptually
+ * infinite surface, but each ThebesLayer has an associated "valid region"
+ * of contents that it is currently storing, which is finite. ThebesLayer
+ * implementations can store content between paints.
+ * 
+ * ThebesLayers are rendered into during the drawing phase of a transaction.
+ *
+ * Currently the contents of a ThebesLayer are in the device output color
+ * space.
+ */
+class THEBES_API ThebesLayer : public Layer {
+public:
+  /**
+   * CONSTRUCTION PHASE ONLY
+   * Tell this layer that the content in some region has changed and
+   * will need to be repainted. This area is removed from the valid
+   * region.
+   */
+  virtual void InvalidateRegion(const nsIntRegion& aRegion) = 0;
+
+  /**
+   * DRAWING PHASE ONLY
+   * Start drawing into the layer. On return, aRegionToDraw contains the
+   * region that needs to be drawn in by the caller. This would normally
+   * be a subregion of the visible region. Drawing is not necessarily
+   * clipped to aRegionToDraw.
+   * 
+   * No other layer operations are allowed until we call EndDrawing on this
+   * layer. During the drawing phase, all ThebesLayers in the tree must be
+   * drawn in tree order, exactly once each, except for those layers
+   * where it is known that the visible region is empty. (Calling
+   * BeginDrawing on non-visible layers is allowed, but aRegionToDraw
+   * will return empty.)
+   * 
+   * When an empty region is returned in aRegionToDraw, BeginDrawing
+   * may return a null context.
+   * 
+   * The layer system will hold a reference to the returned gfxContext*
+   * until EndDrawing is called. The returned gfxContext must not be used
+   * after EndDrawing is called.
+   */
+  virtual gfxContext* BeginDrawing(nsIntRegion* aRegionToDraw) = 0;
+  /**
+   * DRAWING PHASE ONLY
+   * We've finished drawing into this layer. At this point the caller
+   * must have drawn all of aRegionToDraw that was returned by
+   * BeginDrawing, and we guarantee that buffered contents in the visible
+   * region are now valid.
+   */
+  virtual void EndDrawing() = 0;
+
+  /**
+   * DRAWING PHASE ONLY
+   * Copy the aRegion contents from aSource into this layer, offsetting
+   * them by aDelta. The validity is also copied, so invalid areas in
+   * aSource will make corresponding areas of this layer invalid. You
+   * must not call this after BeginDrawing/EndDrawing on this layer.
+   * 
+   * aSource must be this layer or a layer after this layer in a
+   * preorder traversal of the layer tree.
+   */
+  virtual void CopyFrom(ThebesLayer* aSource,
+                        const nsIntRegion& aRegion,
+                        const nsIntPoint& aDelta) = 0;
+
+protected:
+  ThebesLayer(LayerManager* aManager, void* aImplData)
+    : Layer(aManager, aImplData) {}
+};
+
+/**
+ * A Layer which other layers render into. It holds references to its
+ * children.
+ */
+class THEBES_API ContainerLayer : public Layer {
+public:
+  /**
+   * CONSTRUCTION PHASE ONLY
+   * Insert aChild into the child list of this container. aChild must
+   * not be currently in any child list or the root for the layer manager.
+   * If aAfter is non-null, it must be a child of this container and
+   * we insert after that layer. If it's null we insert at the start.
+   */
+  virtual void InsertAfter(Layer* aChild, Layer* aAfter) = 0;
+  /**
+   * CONSTRUCTION PHASE ONLY
+   * Remove aChild from the child list of this container. aChild must
+   * be a child of this container.
+   */
+  virtual void RemoveChild(Layer* aChild) = 0;
+
+  // This getter can be used anytime.
+  virtual Layer* GetFirstChild() { return mFirstChild; }
+
+protected:
+  ContainerLayer(LayerManager* aManager, void* aImplData)
+    : Layer(aManager, aImplData),
+      mFirstChild(nsnull)
+  {}
+
+  Layer* mFirstChild;
+};
+
+}
+}
+
+#endif /* GFX_LAYERS_H */

new file mode 100644
--- /dev/null
+++ b/gfx/layers/Makefile.in
@@ -0,0 +1,69 @@
+#
+# ***** 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 Corporation code.
+#
+# The Initial Developer of the Original Code is Mozilla Foundation.
+# Portions created by the Initial Developer are Copyright (C) 2009
+# the Initial Developer. All Rights Reserved.
+#
+# Contributor(s):
+#   Robert O'Callahan <robert@ocallahan.org>
+#
+# Alternatively, the contents of this file may be used under the terms of
+# either of 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 *****
+
+DEPTH       = ../..
+topsrcdir   = @top_srcdir@
+srcdir      = @srcdir@
+VPATH       = @srcdir@
+
+include $(DEPTH)/config/autoconf.mk
+
+MODULE         = layers
+LIBRARY_NAME   = layers
+EXPORT_LIBRARY = 1
+LIBXUL_LIBRARY = 1
+
+EXPORTS = \
+        Layers.h \
+        $(NULL)
+
+CPPSRCS = \
+        $(NULL)
+
+EXTRA_DSO_LIBS = \
+        gkgfx \
+        thebes \
+        $(NULL)
+
+EXTRA_DSO_LDOPTS += \
+        $(EXTRA_DSO_LIBS) \
+        $(MOZ_CAIRO_LIBS) \
+        $(XPCOM_LIBS) \
+        $(NSPR_LIBS) \
+        $(NULL)
+
+include $(topsrcdir)/config/rules.mk

--- a/toolkit/toolkit-makefiles.sh
+++ b/toolkit/toolkit-makefiles.sh
@@ -116,16 +116,17 @@ MAKEFILES_xmlparser="
   parser/xml/Makefile
   parser/xml/public/Makefile
   parser/xml/src/Makefile
 "
 
 MAKEFILES_gfx="
   gfx/Makefile
   gfx/idl/Makefile
+  gfx/layers/Makefile
   gfx/public/Makefile
   gfx/src/Makefile
   gfx/src/psshared/Makefile
   gfx/src/thebes/Makefile
   gfx/tests/Makefile
   gfx/thebes/Makefile
   gfx/thebes/public/Makefile
   gfx/thebes/src/Makefile