Raise the loading priority of in-viewport images.

Source/core/fetch/ResourceLoadPriorityOptimizer.h

Index: Source/core/fetch/ResourceLoadPriorityOptimizer.h
diff --git a/Source/core/rendering/SubtreeLayoutScope.h b/Source/core/fetch/ResourceLoadPriorityOptimizer.h
similarity index 65%
copy from Source/core/rendering/SubtreeLayoutScope.h
copy to Source/core/fetch/ResourceLoadPriorityOptimizer.h
index c073b7f4cf1e801517c5e8654504b7f3b3ae7ed7..cb58320a410b54afd1fba7bbe4957f039092f55c 100644
--- a/Source/core/rendering/SubtreeLayoutScope.h
+++ b/Source/core/fetch/ResourceLoadPriorityOptimizer.h
@@ -28,41 +28,40 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
-#ifndef SubtreeLayoutScope_h
-#define SubtreeLayoutScope_h
+#ifndef ResourceLoadPriorityOptimizer_h
+#define ResourceLoadPriorityOptimizer_h
 
-#include "wtf/HashSet.h"
+#include "core/fetch/ImageResource.h"
+#include "core/fetch/ResourcePtr.h"
+#include "platform/geometry/LayoutRect.h"
 
-// This is the way to mark a subtree as needing layout during layout,
-// e.g. for the purposes of doing a multipass layout.
-//
-// It should only be used during layout. Outside of layout, you should
-// just call renderer->setNeedsLayout() directly.
-//
-// It ensures that you don't accidentally mark part of the tree as
-// needing layout and not actually lay it out.
+#include "wtf/HashMap.h"
+#include "wtf/OwnPtr.h"
 
 namespace WebCore {
 
-class RenderObject;
-
-class SubtreeLayoutScope {
+class ResourceLoadPriorityOptimizer {
 public:
-    SubtreeLayoutScope(RenderObject* root);
-    ~SubtreeLayoutScope();
-
-    void setNeedsLayout(RenderObject* descendant);
-    void setChildNeedsLayout(RenderObject* descendant);
-
-    RenderObject* root() { return m_root; }
-    void addRendererToLayout(RenderObject* renderer);
+    enum VisibilityStatus {
+        NotVisible,
+        Visible,
+    };
+    ResourceLoadPriorityOptimizer();
+    ~ResourceLoadPriorityOptimizer();
+    void notifyImageResourceVisibility(ImageResource*, VisibilityStatus);
 
 private:
-    RenderObject* m_root;
+    void updateImageResourcesWithLoadPriority();
 
-#ifndef NDEBUG
-    HashSet<RenderObject*> m_renderersToLayout;
-#endif
+    struct ResourceAndVisibility {
+        ResourceAndVisibility(ImageResource*, VisibilityStatus);
+        ~ResourceAndVisibility();
+        ResourcePtr<ImageResource> imageResource;
+        VisibilityStatus status;
+    };
+
+    typedef HashMap<unsigned long, OwnPtr<ResourceAndVisibility> > ImageResourceMap;
+    ImageResourceMap m_imageResources;
 };
 
 }