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 5f0eb9c7f4b07ca76caf9e01d55a68562f1ef96b..59f4a000cb9483c64b83a26a76e7f8a02b4855d3 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"
@@ -58,6 +59,8 @@
 #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 "platform/graphics/GraphicsContextStateSaver.h"
@@ -1252,6 +1255,82 @@ 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;
+
+    Vector<ImageResource*> images;

[shatch, 2013/12/07 03:16:15]

Reorganized this function to grab the images out of the style first, and if
there are none then early exit to avoid having to compute the RenderObject's
bounds and grabbing the view rect. This brought the float tests back to normal.

+
+    for (const FillLayer* layer = blockStyle->backgroundLayers(); layer; layer = layer->next()) {

[shatch, 2013/12/07 03:16:15]

Swapped the ::access<func> for these (::backgroundLayers() and ::maskLayers())
since the access functions can potentially do copies. This brought the ShadowDom
perf test back to normal.

+        if (layer->image()) {
+            ImageResource* img = layer->image()->cachedImage();
+            if (img) {
+                images.append(img);
+            }
+        }
+    }
+    for (const FillLayer* layer = blockStyle->maskLayers(); layer; layer = layer->next()) {
+        if (layer->image()) {
+            ImageResource* imageResource = layer->image()->cachedImage();
+            if (imageResource) {
+                images.append(imageResource);
+            }
+        }
+    }
+    ContentData* contentData = const_cast<ContentData*>(blockStyle->contentData());
+    if (contentData && contentData->isImage()) {
+        ImageContentData* imageContentData = static_cast<ImageContentData*>(contentData);
+        if (imageContentData->image() && imageContentData->image()->cachedImage())
+            images.append(imageContentData->image()->cachedImage());
+    }
+    if (blockStyle->boxReflect()) {
+        if (blockStyle->boxReflect()->mask().image()) {
+            if (blockStyle->boxReflect()->mask().image()->cachedImage()) {
+                images.append(blockStyle->boxReflect()->mask().image()->cachedImage());
+            }
+        }
+    }
+    if (blockStyle->listStyleImage() && blockStyle->listStyleImage()->cachedImage())
+        images.append(blockStyle->listStyleImage()->cachedImage());
+    if (blockStyle->borderImageSource() && blockStyle->borderImageSource()->cachedImage())
+        images.append(blockStyle->borderImageSource()->cachedImage());
+    if (blockStyle->maskBoxImageSource() && blockStyle->maskBoxImageSource()->cachedImage())
+        images.append(blockStyle->maskBoxImageSource()->cachedImage());
+
+    if (images.isEmpty())
+        return;
+
+    const LayoutRect& viewBounds = viewRect();
+    LayoutRect objectBounds = absoluteContentBox();
+    // 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 (Vector<ImageResource*>::iterator it = images.begin(), end = images.end(); it != end; ++it)
+        optimizer.notifyImageResourceVisibility(*it, status);
+}
+
 void RenderBlock::relayoutShapeDescendantIfMoved(RenderBlock* child, LayoutSize offset)
 {
     LayoutUnit left = isHorizontalWritingMode() ? offset.width() : offset.height();