diff -r 000000000000 -r 6474c204b198 gfx/layers/LayerTreeInvalidation.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gfx/layers/LayerTreeInvalidation.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,72 @@
+/*-*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * 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/. */
+
+#ifndef GFX_LAYER_TREE_INVALIDATION_H
+#define GFX_LAYER_TREE_INVALIDATION_H
+
+#include "nsRegion.h"                   // for nsIntRegion
+
+class nsPresContext;
+struct nsIntPoint;
+
+namespace mozilla {
+namespace layers {
+
+class Layer;
+class ContainerLayer;
+
+/**
+ * Callback for ContainerLayer invalidations.
+ *
+ * @param aContainer ContainerLayer being invalidated.
+ * @param aRegion Invalidated region in the ContainerLayer's coordinate
+ * space.
+ */
+typedef void (*NotifySubDocInvalidationFunc)(ContainerLayer* aLayer,
+                                             const nsIntRegion& aRegion);
+
+/**
+ * A set of cached layer properties (including those of child layers),
+ * used for comparing differences in layer trees.
+ */
+struct LayerProperties
+{
+  virtual ~LayerProperties() {}
+
+  /**
+   * Copies the current layer tree properties into
+   * a new LayerProperties object.
+   *
+   * @param Layer tree to copy, or nullptr if we have no 
+   * initial layer tree.
+   */
+  static LayerProperties* CloneFrom(Layer* aRoot);
+
+  /**
+   * Clear all invalidation status from this layer tree.
+   */
+  static void ClearInvalidations(Layer* aRoot);
+
+  /**
+   * Compares a set of existing layer tree properties to the current layer
+   * tree and generates the changed rectangle.
+   *
+   * @param aRoot Root layer of the layer tree to compare against.
+   * @param aCallback If specified, callback to call when ContainerLayers
+   * are invalidated.
+   * @return Painted area changed by the layer tree changes.
+   */
+  virtual nsIntRegion ComputeDifferences(Layer* aRoot, 
+                                         NotifySubDocInvalidationFunc aCallback,
+                                         bool* aGeometryChanged = nullptr) = 0;
+  
+  
+  virtual void MoveBy(const nsIntPoint& aOffset) = 0;
+};
+
+} // namespace layers
+} // namespace mozilla
+
+#endif /* GFX_LAYER_TREE_INVALIDATON_H */