[Slimming Paint] Paint the inspector overlay with GraphicsLayer DisplayList.

Source/web/PageOverlayList.h

Index: Source/web/PageOverlayList.h
diff --git a/Source/web/PageOverlayList.h b/Source/web/PageOverlayList.h
index 779a7db74d9a4d4bf90b5b475a07e656f639c1db..33822df83825a9814fbed647b17b1f390223890e 100644
--- a/Source/web/PageOverlayList.h
+++ b/Source/web/PageOverlayList.h
@@ -29,6 +29,7 @@
 #ifndef PageOverlayList_h
 #define PageOverlayList_h
 
+#include "web/PageOverlay.h"
 #include "wtf/OwnPtr.h"
 #include "wtf/PassOwnPtr.h"
 #include "wtf/Vector.h"
@@ -51,14 +52,21 @@ public:
 
     // Adds/removes a PageOverlay for given client.
     // Returns true if a PageOverlay is added/removed.
-    bool add(WebPageOverlay*, int /* zOrder */);
+    bool add(WebPageOverlay*, int zOrder);
+    bool add(PageOverlay::Painter*, int zOrder);
     bool remove(WebPageOverlay*);
+    bool remove(PageOverlay::Painter*);
 
     void update();
     void paintWebFrame(GraphicsContext&);
 
     size_t findGraphicsLayer(GraphicsLayer*);
 
+    // FIXME: Really, it should be possible for there to be multiple.
+    // But the signature of WebViewImpl::setOverlayLayer already seems to
+    // preclude that.
+    GraphicsLayer* graphicsLayerForTesting() const;
+
 private:
     typedef Vector<OwnPtr<PageOverlay>, 2> PageOverlays;
 
@@ -66,6 +74,14 @@ private:
 
     // Returns the index of the client found. Otherwise, returns WTF::kNotFound.
     size_t find(WebPageOverlay*);
+    size_t find(PageOverlay::Painter*);
+
+    // Finds the overlay with the given client, adding it if it does not exist.
+    template <typename T>
+    size_t findOrAdd(T* client, bool& added);
+
+    // Adjusts overlay order to match z-order and issue any necessary updates.
+    void updateForZOrder(size_t indexOfChangedOverlay);
 
     WebViewImpl* m_viewImpl;
     PageOverlays m_pageOverlays;