Add infrastructure for partial layouts

Source/core/page/FrameView.h

Index: Source/core/page/FrameView.h
diff --git a/Source/core/page/FrameView.h b/Source/core/page/FrameView.h
index 3e77cc62cb3586a92fcc12725744734b5cdf70fe..6f88d5ab7f696444e4badac638db7bbc86026e80 100644
--- a/Source/core/page/FrameView.h
+++ b/Source/core/page/FrameView.h
@@ -335,6 +335,11 @@ public:
     // DEPRECATED: Use viewportConstrainedVisibleContentRect() instead.
     IntSize scrollOffsetForFixedPosition() const;
 
+    bool shouldStopPartialLayout() const { return m_shouldStopPartialLayout; }
+    bool checkPartialLayoutComplete(RenderObject*);
+    void setStopLayoutAtRenderer(RenderObject* renderer) { m_stopLayoutAtRenderer = renderer; }
+    void resetPartialLayoutState() { m_stopLayoutAtRenderer = 0; m_shouldStopPartialLayout = false; }
+
 protected:
     virtual bool scrollContentsFastPath(const IntSize& scrollDelta, const IntRect& rectToScroll, const IntRect& clipRect);
     virtual void scrollContentsSlowPath(const IntRect& updateRect);
@@ -420,6 +425,10 @@ private:
     virtual AXObjectCache* axObjectCache() const;
     void removeFromAXObjectCache();
 
+#ifndef NDEBUG
+    void checkPartialLayoutAllowed();
+#endif
+
     static double s_currentFrameTimeStamp; // used for detecting decoded resource thrash in the cache
     static bool s_inPaintContents;
 
@@ -528,8 +537,26 @@ private:
     bool m_hasSoftwareFilters;
 
     float m_visibleContentScaleFactor;
+
+    bool m_shouldStopPartialLayout;
+    RenderObject* m_stopLayoutAtRenderer;
 };
 
+inline bool FrameView::checkPartialLayoutComplete(RenderObject* renderer)
+{
+    if (m_shouldStopPartialLayout)
+        return true;
+
+    if (renderer == m_stopLayoutAtRenderer) {
+#ifndef NDEBUG
+        checkPartialLayoutAllowed();
+#endif
+        m_shouldStopPartialLayout = true;

[eseidel, 2013/08/20 21:00:39]

I think when you do this, you should also clear m_stopLayoutAtRenderer.  We've
transitioned from the phase of "should we stop" to "we're stopping" and then
when we hit "stopped" we'll even clear the "we're stopping" bool.

[pdr., 2013/08/26 05:50:40]

Done.

+        return true;
+    }
+    return false;
+}
+
 inline void FrameView::incrementVisuallyNonEmptyCharacterCount(unsigned count)
 {
     if (m_isVisuallyNonEmpty)