[WIP] Adding support for <iframe>s to slimming paint.

Source/core/frame/FrameView.h

Index: Source/core/frame/FrameView.h
diff --git a/Source/core/frame/FrameView.h b/Source/core/frame/FrameView.h
index f2e56f68f001f9a35704c170439738442bf3cef0..689e544215cd97ec55fd5eb205790ffacb06d9c1 100644
--- a/Source/core/frame/FrameView.h
+++ b/Source/core/frame/FrameView.h
@@ -26,6 +26,7 @@
 #define FrameView_h
 
 #include "core/frame/FrameViewAutoSizeInfo.h"
+#include "core/paint/ViewDisplayList.h"
 #include "core/rendering/PaintPhase.h"
 #include "platform/RuntimeEnabledFeatures.h"
 #include "platform/Widget.h"
@@ -517,6 +518,15 @@ public:
 
     void calculateOverhangAreasForPainting(IntRect& horizontalOverhangRect, IntRect& verticalOverhangRect);
 
+    ViewDisplayList& viewDisplayList()

[chrishtr, 2014/11/01 23:44:10]

Don't inline this.

[trchen, 2014/11/02 10:36:46]

Acknowledged.

+    {
+        ASSERT(RuntimeEnabledFeatures::slimmingPaintEnabled());
+        ASSERT(frame().isLocalRoot());
+        if (!m_viewDisplayList)
+            m_viewDisplayList = adoptPtr(new ViewDisplayList());
+        return *m_viewDisplayList;
+    }
+
 protected:
     // Scroll the content via the compositor.
     bool scrollContentsFastPath(const IntSize& scrollDelta);
@@ -778,6 +788,8 @@ private:
     bool m_shouldDrawPanScrollIcon;
 
     bool m_clipsRepaints;
+
+    OwnPtr<ViewDisplayList> m_viewDisplayList;
 };
 
 inline void FrameView::incrementVisuallyNonEmptyCharacterCount(unsigned count)