Common up SVG transform "change detection" (classification)

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

Index: third_party/WebKit/Source/core/layout/svg/LayoutSVGViewportContainer.cpp
diff --git a/third_party/WebKit/Source/core/layout/svg/LayoutSVGViewportContainer.cpp b/third_party/WebKit/Source/core/layout/svg/LayoutSVGViewportContainer.cpp
index b4ab298affd99d79346b5c3546521f41a6603a7b..e4662411b9258937c5cf25bf98e7bf117c5d2b0a 100644
--- a/third_party/WebKit/Source/core/layout/svg/LayoutSVGViewportContainer.cpp
+++ b/third_party/WebKit/Source/core/layout/svg/LayoutSVGViewportContainer.cpp
@@ -70,21 +70,15 @@ void LayoutSVGViewportContainer::setNeedsTransformUpdate()
     m_needsTransformUpdate = true;
 }
 
-static std::pair<double, double> scaleReference(const AffineTransform& transform)
-{
-    return std::make_pair(transform.xScaleSquared(), transform.yScaleSquared());
-}
-
-LayoutSVGContainer::TransformChange LayoutSVGViewportContainer::calculateLocalTransform()
+SVGTransformChange LayoutSVGViewportContainer::calculateLocalTransform()
 {
     if (!m_needsTransformUpdate)
-        return TransformChange::None;
+        return SVGTransformChange::None;
 
-    std::pair<double, double> oldScale = scaleReference(m_localToParentTransform);
+    SVGTransformChangeDetector changeDetector(m_localToParentTransform);
     m_localToParentTransform = AffineTransform::translation(m_viewport.x(), m_viewport.y()) * viewportTransform();
     m_needsTransformUpdate = false;
-    return scaleReference(m_localToParentTransform) != oldScale
-        ? TransformChange::Full : TransformChange::ScaleInvariant;
+    return changeDetector.computeChange(m_localToParentTransform);
 }
 
 AffineTransform LayoutSVGViewportContainer::viewportTransform() const