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..340c1c43279cadbc8cb93c7398c4b711c5a212eb 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"
@@ -169,6 +172,12 @@ static void removeBlockFromDescendantAndContainerMaps(RenderBlock* block, Tracke
     }
 }
 
+static void appendImageResourceIfNotNull(Vector<ImageResource*>& imageResources, ImageResource* imageResource)
+{
+    if (imageResource)
+        imageResources.append(imageResource);
+}
+
 RenderBlock::~RenderBlock()
 {
     if (hasColumns())
@@ -1252,6 +1261,72 @@ 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;
+
+    const FillLayer* styleLayers[2] = {blockStyle->backgroundLayers(), blockStyle->maskLayers()};
+    for (int i = 0; i < 2; ++i) {
+        for (const FillLayer* layer = styleLayers[i]; layer; layer = layer->next()) {

[eseidel, 2013/12/10 17:15:30]

Oh, I see.  I had envisoned:

appendLayers(images, blockStyle->backgroundLayers());
appendLayers(images, blockStyle->maskLayers());

[shatch, 2013/12/10 18:56:19]

Done.

+            if (layer->image()) {

[eseidel, 2013/12/10 17:15:30]

nit: This could now drop at least the inner {}

[shatch, 2013/12/10 18:56:19]

Done.

+                appendImageResourceIfNotNull(images, layer->image()->cachedImage());
+            }
+        }
+    }
+    ContentData* contentData = const_cast<ContentData*>(blockStyle->contentData());

[eseidel, 2013/12/10 17:15:30]

The const disease!

[shatch, 2013/12/10 18:56:19]

Oops, yeah doesn't even need to be cast.

+    if (contentData && contentData->isImage()) {
+        ImageContentData* imageContentData = static_cast<ImageContentData*>(contentData);

[eseidel, 2013/12/10 17:15:30]

I'm surprised we don't have a toImageContentData() helper yet.  Those seem to be
all the rage in Blink these days.

+        if (imageContentData->image())
+            appendImageResourceIfNotNull(images, imageContentData->image()->cachedImage());
+    }
+    if (blockStyle->boxReflect()) {

[eseidel, 2013/12/10 17:15:30]

nit: These two ifs could now combine into one line and drop the {}

[shatch, 2013/12/10 18:56:19]

Done.

+        if (blockStyle->boxReflect()->mask().image()) {
+            appendImageResourceIfNotNull(images, blockStyle->boxReflect()->mask().image()->cachedImage());
+        }
+    }
+    if (blockStyle->listStyleImage())

[eseidel, 2013/12/10 17:15:30]

You could even push this check inside if you like.  This is an Image*?

[eseidel, 2013/12/10 17:17:05]

By this I mean:
appendImageIfNotNull(images, blockSTyle->borderImageSource());
appendImageIfNotNull(images, blockStyle->maskImageSource());
appendImageIfNotNull(images, blockStyle->listStyleImage());

[shatch, 2013/12/10 18:56:19]

Done.

+        appendImageResourceIfNotNull(images, blockStyle->listStyleImage()->cachedImage());
+    if (blockStyle->borderImageSource())
+        appendImageResourceIfNotNull(images, blockStyle->borderImageSource()->cachedImage());
+    if (blockStyle->maskBoxImageSource())
+        appendImageResourceIfNotNull(images, blockStyle->maskBoxImageSource()->cachedImage());
+
+    if (images.isEmpty())
+        return;
+
+    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())

[eseidel, 2013/12/10 17:15:30]

I'd just pick the behavior you want for empty rects and short-circut here  Like
I would just say that all empty rects are pretended to be invisible always.  if
(objectBounds.isEmpty()) return;

[shatch, 2013/12/10 18:56:19]

Addressed in other comment in RenderImage.

+        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();