Use new downcast helper for blink::SVGTSpanElement

This CL has goal to use IsA<SVGTSpanElement>(element) in place of
IsSVGTSpanElement(element)

Bug: 891908
Change-Id: Idae91831dfddadf9fe83ff26ce4689a336dac05d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1936624
Commit-Queue: Abhijeet | Igalia <abhijeet@igalia.com>
Reviewed-by: Jeremy Roman <jbroman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#720344}

third_party/blink/renderer/core/css/resolver/style_adjuster.cc

@@ -696,7 +696,7 @@ void StyleAdjuster::AdjustComputedStyle(StyleResolverState& state,
     if (style.Display() == EDisplay::kContents &&
         (is_svg_root ||
          (!IsA<SVGSVGElement>(element) && !IsSVGGElement(element) &&
-          !IsA<SVGUseElement>(element) && !IsSVGTSpanElement(element)))) {
+          !IsA<SVGUseElement>(element) && !IsA<SVGTSpanElement>(element)))) {
       // According to the CSS Display spec[1], nested <svg> elements, <g>,
       // <use>, and <tspan> elements are not rendered and their children are
       // "hoisted". For other elements display:contents behaves as display:none.

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

@@ -37,7 +37,7 @@ bool SVGTSpanElement::LayoutObjectIsNeeded(const ComputedStyle& style) const {
   if (parentNode() &&
       (IsSVGAElement(*parentNode()) || IsA<SVGTextElement>(*parentNode()) ||
        IsA<SVGTextPathElement>(*parentNode()) ||
-       IsSVGTSpanElement(*parentNode())))
+       IsA<SVGTSpanElement>(*parentNode())))
     return SVGElement::LayoutObjectIsNeeded(style);
 
   return false;