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 017a1e0aa33d6f4e897ea1394f5fd069803d157d..ae636a64ac2f90c88cf3443058bb6dbd1220e2e4 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; }
+    void checkPartialLayoutComplete(RenderObject*);
+    void setStopLayoutAtRenderer(RenderObject* renderer) { m_stopLayoutAtRenderer = renderer; }
+    void resetPartialLayoutState() { m_stopLayoutAtRenderer = 0; m_shouldStopPartialLayout = false; }

[esprehn, 2013/08/18 03:43:15]

Isn't shouldStopPartialLayout the same as checking if stopLayoutAtRenderer is
not null? Why do you need a boolean?

[pdr., 2013/08/20 06:19:10]

We need the boolean to track that we're exiting in the middle of layout.

m_stopLayoutAtRenderer is used to determine which renderer we need to stop
layout on.
m_shouldStopPartialLayout is used to say 'STOP' to all the layout methods.

In a full, complete layout, m_stopLayoutAtRenderer will be 0 and
m_shouldStopPartialLayout will be false.
In a partial layout, before we've laid out the target renderer,
m_shouldStopPartialLayout will be false.
In a partial layout, after we've laid out the target renderer,
m_shouldStopPartialLayout will be true.

Happy to update these names if we can make this more understandable. One idea is
to move this state into a small struct or class such as PartialLayoutState to
hide some of these details. We could also hide some kind of
temporarilyDisablePartialLayout functionality in a class for working around
two-pass layouts.

+
 protected:
     virtual bool scrollContentsFastPath(const IntSize& scrollDelta, const IntRect& rectToScroll, const IntRect& clipRect);
     virtual void scrollContentsSlowPath(const IntRect& updateRect);
@@ -526,6 +531,9 @@ private:
     bool m_hasSoftwareFilters;
 
     float m_visibleContentScaleFactor;
+
+    bool m_shouldStopPartialLayout;
+    RenderObject* m_stopLayoutAtRenderer;
 };
 
 inline void FrameView::incrementVisuallyNonEmptyCharacterCount(unsigned count)