Raise the loading priority of in-viewport images.

Source/core/fetch/ResourceLoadPriorityOptimizer.cpp

Index: Source/core/fetch/ResourceLoadPriorityOptimizer.cpp
diff --git a/Source/core/rendering/SubtreeLayoutScope.cpp b/Source/core/fetch/ResourceLoadPriorityOptimizer.cpp
similarity index 53%
copy from Source/core/rendering/SubtreeLayoutScope.cpp
copy to Source/core/fetch/ResourceLoadPriorityOptimizer.cpp
index d650513a1c89e451b77d327e77d8809077432bf9..29882526a7c3c9c29648936219152a8f0d5d5aef 100644
--- a/Source/core/rendering/SubtreeLayoutScope.cpp
+++ b/Source/core/fetch/ResourceLoadPriorityOptimizer.cpp
@@ -29,52 +29,51 @@
  */
 
 #include "config.h"
-#include "core/rendering/SubtreeLayoutScope.h"
-
-#include "core/frame/FrameView.h"
-#include "core/rendering/RenderObject.h"
+#include "core/fetch/ResourceLoadPriorityOptimizer.h"
 
 namespace WebCore {
 
-SubtreeLayoutScope::SubtreeLayoutScope(RenderObject* root)
-    : m_root(root)
+ResourceLoadPriorityOptimizer::ResourceAndVisibility::ResourceAndVisibility(ImageResource* image, VisibilityStatus v)
+    : imageResource(image)
+    , status(v)
 {
-    RELEASE_ASSERT(m_root->document().view()->isInLayout());
 }
 
-SubtreeLayoutScope::~SubtreeLayoutScope()
+ResourceLoadPriorityOptimizer::ResourceAndVisibility::~ResourceAndVisibility()
 {
-    // Partial layout early-exits layout and will leave the tree as needing layout.
-    if (m_root->frameView()->partialLayout().isStopping()) {
-        ASSERT(m_root->needsLayout());
-        return;
-    }
-
-    RELEASE_ASSERT(!m_root->needsLayout());
+}
 
-#ifndef NDEBUG
-    for (HashSet<RenderObject*>::iterator it = m_renderersToLayout.begin(); it != m_renderersToLayout.end(); ++it)
-        (*it)->assertRendererLaidOut();
-#endif
+ResourceLoadPriorityOptimizer::ResourceLoadPriorityOptimizer()
+{
 }
 
-void SubtreeLayoutScope::setNeedsLayout(RenderObject* descendant)
+ResourceLoadPriorityOptimizer::~ResourceLoadPriorityOptimizer()
 {
-    ASSERT(descendant->isDescendantOf(m_root));
-    descendant->setNeedsLayout(MarkContainingBlockChain, this);
+    updateImageResourcesWithLoadPriority();
 }
 
-void SubtreeLayoutScope::setChildNeedsLayout(RenderObject* descendant)
+void ResourceLoadPriorityOptimizer::updateImageResourcesWithLoadPriority()
 {
-    ASSERT(descendant->isDescendantOf(m_root));
-    descendant->setChildNeedsLayout(MarkContainingBlockChain, this);
+    for (ImageResourceMap::iterator it = m_imageResources.begin(); it != m_imageResources.end(); ++it) {
+        ResourceLoadPriority priority = it->value->status == Visible ?
+            ResourceLoadPriorityLow : ResourceLoadPriorityVeryLow;
+
+        if (priority != it->value->imageResource->resourceRequest().priority()) {
+            it->value->imageResource->resourceRequest().setPriority(priority);
+            it->value->imageResource->didChangePriority(priority);
+        }
+    }
+    m_imageResources.clear();
 }
 
-void SubtreeLayoutScope::addRendererToLayout(RenderObject* renderer)
+void ResourceLoadPriorityOptimizer::notifyImageResourceVisibility(ImageResource* img, VisibilityStatus status)
 {
-#ifndef NDEBUG
-    m_renderersToLayout.add(renderer);
-#endif
+    if (!img || img->isLoaded())
+        return;
+
+    ImageResourceMap::AddResult result = m_imageResources.add(img->identifier(), adoptPtr(new ResourceAndVisibility(img, status)));
+    if (!result.isNewEntry && status == Visible)
+        result.iterator->value->status = status;
 }
 
 }