Split-out change for https://codereview.chromium.org/1145993002/ patch set 11

Source/core/layout/LayoutView.cpp

Index: Source/core/layout/LayoutView.cpp
diff --git a/Source/core/layout/LayoutView.cpp b/Source/core/layout/LayoutView.cpp
index 66e7c764e20d271e8b2f3a9db35012cc709631ed..71f8f06ac67bdc4125aee779cacd12112b3299b3 100644
--- a/Source/core/layout/LayoutView.cpp
+++ b/Source/core/layout/LayoutView.cpp
@@ -219,8 +219,6 @@ void LayoutView::layout()
 
     SubtreeLayoutScope layoutScope(*this);
 
-    LayoutRect oldLayoutOverflowRect = layoutOverflowRect();
-
     // Use calcWidth/Height to get the new width/height, since this will take the full page zoom factor into account.
     bool relayoutChildren = !shouldUsePrintingLayout() && (!m_frameView
         || logicalWidth() != viewLogicalWidthForBoxSizing()
@@ -252,22 +250,64 @@ void LayoutView::layout()
 
     layoutContent();
 
-    if (RuntimeEnabledFeatures::slimmingPaintEnabled() && layoutOverflowRect() != oldLayoutOverflowRect) {
-        // The document element paints the viewport background, so we need to invalidate it when
-        // layout overflow changes.
-        // FIXME: Improve viewport background styling/invalidation/painting. crbug.com/475115
-        if (Element* documentElement = document().documentElement()) {
-            if (LayoutObject* rootObject = documentElement->layoutObject())
-                rootObject->setShouldDoFullPaintInvalidation();
-        }
-    }
-
 #if ENABLE(ASSERT)
     checkLayoutState();
 #endif
     clearNeedsLayout();
 }
 
+void LayoutView::styleDidChange(StyleDifference diff, const ComputedStyle* oldStyle)
+{
+    const ComputedStyle& newStyle = styleRef();
+
+    if (oldStyle && oldStyle->hasEntirelyFixedBackground() != newStyle.hasEntirelyFixedBackground())
+        compositor()->setNeedsUpdateFixedBackground();
+
+    LayoutBlockFlow::styleDidChange(diff, oldStyle);
+}
+
+PaintInvalidationReason LayoutView::invalidatePaintIfNeeded(PaintInvalidationState& paintInvalidationState, const LayoutBoxModelObject& newPaintInvalidationContainer)
+{
+    const LayoutObject* rootObject = document().documentElement() ? document().documentElement()->layoutObject() : nullptr;
+    TransformationMatrix newTransform;
+    LayoutSize newBorderBoxSize;
+    LayoutRect newPaddingBoxRect;
+    LayoutRect newContentBoxRect;
+
+    if (rootObject && rootObject->isBox()) {
+        const LayoutBox& rootBox = toLayoutBox(*rootObject);
+        if (rootBox.hasLayer()) {
+            const DeprecatedPaintLayer& rootLayer = *rootBox.layer();
+            LayoutPoint offset;
+            rootLayer.convertToLayerCoords(nullptr, offset);
+            newTransform.translate(offset.x(), offset.y());
+            newTransform.multiply(rootLayer.currentTransform());
+        }
+        newBorderBoxSize = rootBox.size();
+        newPaddingBoxRect = rootBox.paddingBoxRect();
+        newContentBoxRect = rootBox.contentBoxRect();
+    }
+
+    if (m_previousRootBackgroundPositioning.transform != newTransform)
+        setShouldDoFullPaintInvalidation(PaintInvalidationLocationChange);
+
+    const FillLayer& backgroundLayers = style()->backgroundLayers();
+    if (mustInvalidateFillLayersPaintOnWidthChange(backgroundLayers) || mustInvalidateFillLayersPaintOnHeightChange(backgroundLayers)) {
+        if (m_previousRootBackgroundPositioning.borderBoxSize != newBorderBoxSize
+            || m_previousRootBackgroundPositioning.paddingBoxRect != newPaddingBoxRect
+            || m_previousRootBackgroundPositioning.contentBoxRect != newContentBoxRect) {
+            setShouldDoFullPaintInvalidation(PaintInvalidationBorderBoxChange);
+        }
+    }
+
+    m_previousRootBackgroundPositioning.transform = newTransform;
+    m_previousRootBackgroundPositioning.borderBoxSize = newBorderBoxSize;
+    m_previousRootBackgroundPositioning.paddingBoxRect = newPaddingBoxRect;
+    m_previousRootBackgroundPositioning.contentBoxRect = newContentBoxRect;
+
+    return LayoutBox::invalidatePaintIfNeeded(paintInvalidationState, newPaintInvalidationContainer);
+}
+
 void LayoutView::mapLocalToContainer(const LayoutBoxModelObject* paintInvalidationContainer, TransformState& transformState, MapCoordinatesFlags mode, bool* wasFixed, const PaintInvalidationState* paintInvalidationState) const
 {
     ASSERT_UNUSED(wasFixed, !wasFixed || *wasFixed == static_cast<bool>(mode & IsFixed));