Hoist "layout size changed" check out of SVGLayoutSupport::layoutChildren

third_party/WebKit/Source/core/layout/svg/LayoutSVGRoot.cpp

Index: third_party/WebKit/Source/core/layout/svg/LayoutSVGRoot.cpp
diff --git a/third_party/WebKit/Source/core/layout/svg/LayoutSVGRoot.cpp b/third_party/WebKit/Source/core/layout/svg/LayoutSVGRoot.cpp
index ffed0927bdf87288d605175702123a1bf8c41066..985e24341a7708b8222685c15c214f14c0c63eaa 100644
--- a/third_party/WebKit/Source/core/layout/svg/LayoutSVGRoot.cpp
+++ b/third_party/WebKit/Source/core/layout/svg/LayoutSVGRoot.cpp
@@ -151,12 +151,17 @@ void LayoutSVGRoot::layout()
     SVGSVGElement* svg = toSVGSVGElement(node());
     ASSERT(svg);
     m_isLayoutSizeChanged = needsLayout || (svg->hasRelativeLengths() && oldSize != size());
+    // When hasRelativeLengths() is false, no descendants have relative lengths
+    // (hence no one is interested in viewport size changes).
+    bool layoutSizeChanged = m_isLayoutSizeChanged && svg->hasRelativeLengths();
+
     // If any of this root's children need to be laid out, and a filter is
     // applied to it, we need to issue paint invalidations for all descendants.
     bool forceLayoutOfChildren = needsLayout
         || (normalChildNeedsLayout() && SVGLayoutSupport::hasFilterResource(*this));
+
     const bool transformToRootChanged = false;
-    SVGLayoutSupport::layoutChildren(this, forceLayoutOfChildren, transformToRootChanged);
+    SVGLayoutSupport::layoutChildren(this, forceLayoutOfChildren, transformToRootChanged, layoutSizeChanged);
 
     if (m_needsBoundariesOrTransformUpdate) {
         updateCachedBoundaries();