Raise the loading priority of in-viewport images.

Source/core/rendering/RenderBlock.cpp

Index: Source/core/rendering/RenderBlock.cpp
diff --git a/Source/core/rendering/RenderBlock.cpp b/Source/core/rendering/RenderBlock.cpp
index c76e9acde6d01e090661a14521e89200348cbcd0..72c0b50e3e58bf317ec898e4bd98e63d358ab362 100644
--- a/Source/core/rendering/RenderBlock.cpp
+++ b/Source/core/rendering/RenderBlock.cpp
@@ -32,6 +32,7 @@
 #include "core/dom/shadow/ShadowRoot.h"
 #include "core/editing/Editor.h"
 #include "core/editing/FrameSelection.h"
+#include "core/fetch/ResourceLoadPriorityOptimizer.h"
 #include "core/frame/Frame.h"
 #include "core/frame/FrameView.h"
 #include "core/page/Page.h"
@@ -59,6 +60,8 @@
 #include "core/rendering/RenderTheme.h"
 #include "core/rendering/RenderView.h"
 #include "core/rendering/shapes/ShapeOutsideInfo.h"
+#include "core/rendering/style/ContentData.h"
+#include "core/rendering/style/RenderStyle.h"
 #include "platform/geometry/FloatQuad.h"
 #include "platform/geometry/TransformState.h"
 #include "wtf/StdLibExtras.h"
@@ -1259,6 +1262,75 @@ void RenderBlock::layout()
     invalidateBackgroundObscurationStatus();
 }
 
+void RenderBlock::didLayout(ResourceLoadPriorityOptimizer& optimizer)
+{
+    RenderBox::didLayout(optimizer);
+    updateStyleImageLoadingPriorities(optimizer);
+}
+
+void RenderBlock::didScroll(ResourceLoadPriorityOptimizer& optimizer)
+{
+    RenderBox::didScroll(optimizer);
+    updateStyleImageLoadingPriorities(optimizer);
+}
+
+void RenderBlock::updateStyleImageLoadingPriorities(ResourceLoadPriorityOptimizer& optimizer)
+{
+    RenderStyle* blockStyle = style();
+    if (!blockStyle)
+        return;
+
+    LayoutRect objectBounds = absoluteContentBox();
+    LayoutRect viewBounds = viewRect();
+
+    // The object bounds might be empty right now, so intersects will fail since it doesn't deal
+    // with empty rects. Use LayoutRect::contains in that case.
+    bool isVisible;
+    if (!objectBounds.isEmpty())
+        isVisible =  viewBounds.intersects(objectBounds);
+    else
+        isVisible = viewBounds.contains(objectBounds);
+
+    ResourceLoadPriorityOptimizer::VisibilityStatus status = isVisible ?
+        ResourceLoadPriorityOptimizer::Visible : ResourceLoadPriorityOptimizer::NotVisible;
+
+    for (FillLayer* layer = blockStyle->accessBackgroundLayers(); layer; layer = layer->next()) {
+        if (layer->image()) {
+            ImageResource* img = layer->image()->cachedImage();
+            if (img) {
+                optimizer.notifyImageResourceVisibility(img, status);
+            }
+        }
+    }
+    for (FillLayer* layer = blockStyle->accessMaskLayers(); layer; layer = layer->next()) {
+        if (layer->image()) {
+            ImageResource* img = layer->image()->cachedImage();
+            if (img) {
+                optimizer.notifyImageResourceVisibility(img, status);
+            }
+        }
+    }
+    ContentData* contentData = const_cast<ContentData*>(blockStyle->contentData());
+    if (contentData && contentData->isImage()) {
+        ImageContentData* imageContentData = static_cast<ImageContentData*>(contentData);
+        if (imageContentData->image() && imageContentData->image()->cachedImage())
+            optimizer.notifyImageResourceVisibility(imageContentData->image()->cachedImage(), status);
+    }
+    if (blockStyle->boxReflect()) {
+        if (blockStyle->boxReflect()->mask().image()) {
+            if (blockStyle->boxReflect()->mask().image()->cachedImage()) {
+                optimizer.notifyImageResourceVisibility(blockStyle->boxReflect()->mask().image()->cachedImage(), status);
+            }
+        }
+    }
+    if (blockStyle->listStyleImage() && blockStyle->listStyleImage()->cachedImage())
+        optimizer.notifyImageResourceVisibility(blockStyle->listStyleImage()->cachedImage(), status);
+    if (blockStyle->borderImageSource() && blockStyle->borderImageSource()->cachedImage())
+        optimizer.notifyImageResourceVisibility(blockStyle->borderImageSource()->cachedImage(), status);
+    if (blockStyle->maskBoxImageSource() && blockStyle->maskBoxImageSource()->cachedImage())
+        optimizer.notifyImageResourceVisibility(blockStyle->maskBoxImageSource()->cachedImage(), status);
+}
+
 void RenderBlock::relayoutShapeDescendantIfMoved(RenderBlock* child, LayoutSize offset)
 {
     LayoutUnit left = isHorizontalWritingMode() ? offset.width() : offset.height();