Use new downcast helper for blink::SVGRectElement

This CL has goal to use IsA<SVGRectElement>(element) in place of
IsSVGRectElement(element)

Bug: 891908
Change-Id: I859dd6a2b6255c5ca8644b97c019a6eaf85fb3d9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1936618Reviewed-by: Jeremy Roman <jbroman@chromium.org>
Commit-Queue: Abhijeet | Igalia <abhijeet@igalia.com>
Cr-Commit-Position: refs/heads/master@{#720310}

third_party/blink/renderer/core/css/properties/computed_style_utils.cc

@@ -1420,7 +1420,7 @@ static bool IsSVGObjectWithWidthAndHeight(const LayoutObject& layout_object) {
   DCHECK(layout_object.IsSVGChild());
   return layout_object.IsSVGImage() || layout_object.IsSVGForeignObject() ||
          (layout_object.IsSVGShape() &&
-          IsSVGRectElement(layout_object.GetNode()));
+          IsA<SVGRectElement>(layout_object.GetNode()));
 }
 
 FloatSize ComputedStyleUtils::UsedBoxSize(const LayoutObject& layout_object) {

third_party/blink/renderer/core/layout/svg/svg_layout_tree_as_text.cc

@@ -338,7 +338,7 @@ static WTF::TextStream& operator<<(WTF::TextStream& ts,
   const ComputedStyle& style = shape.StyleRef();
   const SVGComputedStyle& svg_style = style.SvgStyle();
 
-  if (IsSVGRectElement(*svg_element)) {
+  if (IsA<SVGRectElement>(*svg_element)) {
     WriteNameValuePair(ts, "x",
                        length_context.ValueForLength(svg_style.X(), style,
                                                      SVGLengthMode::kWidth));

third_party/blink/renderer/core/svg/svg_animate_motion_element.cc

@@ -47,7 +47,7 @@ bool TargetCanHaveMotionTransform(const SVGElement& target) {
   return IsA<SVGGElement>(target) || IsSVGDefsElement(target) ||
          IsA<SVGUseElement>(target) || IsSVGImageElement(target) ||
          IsSVGSwitchElement(target) || IsSVGPathElement(target) ||
-         IsSVGRectElement(target) || IsSVGCircleElement(target) ||
+         IsA<SVGRectElement>(target) || IsSVGCircleElement(target) ||
          IsSVGEllipseElement(target) || IsA<SVGLineElement>(target) ||
          IsA<SVGPolylineElement>(target) || IsA<SVGPolygonElement>(target) ||
          IsSVGTextElement(target) || IsSVGClipPathElement(target) ||

third_party/blink/renderer/core/svg/svg_use_element.cc

@@ -497,7 +497,7 @@ LayoutObject* SVGUseElement::CreateLayoutObject(const ComputedStyle& style,
 }
 
 static bool IsDirectReference(const SVGElement& element) {
-  return IsSVGPathElement(element) || IsSVGRectElement(element) ||
+  return IsSVGPathElement(element) || IsA<SVGRectElement>(element) ||
          IsSVGCircleElement(element) || IsSVGEllipseElement(element) ||
          IsA<SVGPolygonElement>(element) || IsA<SVGPolylineElement>(element) ||
          IsSVGTextElement(element);