diff -r 000000000000 -r 6474c204b198 layout/generic/nsSplittableFrame.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/layout/generic/nsSplittableFrame.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,109 @@
+/* -*- 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/. */
+
+/*
+ * base class for rendering objects that can be split across lines,
+ * columns, or pages
+ */
+
+#ifndef nsSplittableFrame_h___
+#define nsSplittableFrame_h___
+
+#include "mozilla/Attributes.h"
+#include "nsFrame.h"
+
+// Derived class that allows splitting
+class nsSplittableFrame : public nsFrame
+{
+public:
+  NS_DECL_FRAMEARENA_HELPERS
+
+  virtual void Init(nsIContent*      aContent,
+                    nsIFrame*        aParent,
+                    nsIFrame*        aPrevInFlow) MOZ_OVERRIDE;
+  
+  virtual nsSplittableType GetSplittableType() const MOZ_OVERRIDE;
+
+  virtual void DestroyFrom(nsIFrame* aDestructRoot) MOZ_OVERRIDE;
+
+  /*
+   * Frame continuations can be either fluid or not:
+   * Fluid continuations ("in-flows") are the result of line breaking, 
+   * column breaking, or page breaking.
+   * Other (non-fluid) continuations can be the result of BiDi frame splitting.
+   * A "flow" is a chain of fluid continuations.
+   */
+  
+  // Get the previous/next continuation, regardless of its type (fluid or non-fluid).
+  virtual nsIFrame* GetPrevContinuation() const MOZ_OVERRIDE;
+  virtual nsIFrame* GetNextContinuation() const MOZ_OVERRIDE;
+
+  // Set a previous/next non-fluid continuation.
+  virtual void SetPrevContinuation(nsIFrame*) MOZ_OVERRIDE;
+  virtual void SetNextContinuation(nsIFrame*) MOZ_OVERRIDE;
+
+  // Get the first/last continuation for this frame.
+  virtual nsIFrame* FirstContinuation() const MOZ_OVERRIDE;
+  virtual nsIFrame* LastContinuation() const MOZ_OVERRIDE;
+
+#ifdef DEBUG
+  // Can aFrame2 be reached from aFrame1 by following prev/next continuations?
+  static bool IsInPrevContinuationChain(nsIFrame* aFrame1, nsIFrame* aFrame2);
+  static bool IsInNextContinuationChain(nsIFrame* aFrame1, nsIFrame* aFrame2);
+#endif
+  
+  // Get the previous/next continuation, only if it is fluid (an "in-flow").
+  nsIFrame* GetPrevInFlow() const;
+  nsIFrame* GetNextInFlow() const;
+
+  virtual nsIFrame* GetPrevInFlowVirtual() const MOZ_OVERRIDE { return GetPrevInFlow(); }
+  virtual nsIFrame* GetNextInFlowVirtual() const MOZ_OVERRIDE { return GetNextInFlow(); }
+  
+  // Set a previous/next fluid continuation.
+  virtual void SetPrevInFlow(nsIFrame*) MOZ_OVERRIDE;
+  virtual void SetNextInFlow(nsIFrame*) MOZ_OVERRIDE;
+
+  // Get the first/last frame in the current flow.
+  virtual nsIFrame* FirstInFlow() const MOZ_OVERRIDE;
+  virtual nsIFrame* LastInFlow() const MOZ_OVERRIDE;
+
+  // Remove the frame from the flow. Connects the frame's prev-in-flow
+  // and its next-in-flow. This should only be called in frame Destroy() methods.
+  static void RemoveFromFlow(nsIFrame* aFrame);
+
+protected:
+  nsSplittableFrame(nsStyleContext* aContext) : nsFrame(aContext) {}
+
+  /**
+   * Determine the height consumed by our previous-in-flows.
+   *
+   * @note (bz) This makes laying out a splittable frame with N in-flows
+   *       O(N^2)! So, use this function with caution and minimize the number
+   *       of calls to this method.
+   */
+  nscoord GetConsumedHeight() const;
+
+  /**
+   * Retrieve the effective computed height of this frame, which is the computed
+   * height, minus the height consumed by any previous in-flows.
+   */
+  nscoord GetEffectiveComputedHeight(const nsHTMLReflowState& aReflowState,
+                                     nscoord aConsumed = NS_INTRINSICSIZE) const;
+
+  /**
+   * @see nsIFrame::GetLogicalSkipSides()
+   * @see nsIFrame::ApplyLogicalSkipSides()
+   */
+  virtual int GetLogicalSkipSides(const nsHTMLReflowState* aReflowState = nullptr) const MOZ_OVERRIDE;
+
+#ifdef DEBUG
+  virtual void DumpBaseRegressionData(nsPresContext* aPresContext, FILE* out, int32_t aIndent) MOZ_OVERRIDE;
+#endif
+
+  nsIFrame*   mPrevContinuation;
+  nsIFrame*   mNextContinuation;
+};
+
+#endif /* nsSplittableFrame_h___ */