Use new downcast helper for blink::SVGGraphicsElement

Bug: 891908
Change-Id: Id65e5d833e4ccf16df6fa5c15f321b7bd38becb7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1710599
Commit-Queue: Abhijeet Kandalkar <abhijeet@igalia.com>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#679949}

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

@@ -60,7 +60,7 @@ void LayoutSVGPath::UpdateMarkers() {
   marker_positions_.clear();
 
   if (!StyleRef().SvgStyle().HasMarkers() ||
-      !SVGResources::SupportsMarkers(*ToSVGGraphicsElement(GetElement())))
+      !SVGResources::SupportsMarkers(*To<SVGGraphicsElement>(GetElement())))
     return;
 
   SVGResources* resources =

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

@@ -84,9 +84,10 @@ ClipStrategy DetermineClipStrategy(const SVGElement& element) {
     return ModifyStrategyForClipPath(use_layout_object->StyleRef(),
                                      shape_strategy);
   }
-  if (!element.IsSVGGraphicsElement())
+  auto* svg_graphics_element = DynamicTo<SVGGraphicsElement>(element);
+  if (!svg_graphics_element)
     return ClipStrategy::kNone;
-  return DetermineClipStrategy(ToSVGGraphicsElement(element));
+  return DetermineClipStrategy(*svg_graphics_element);
 }
 
 bool ContributesToClip(const SVGElement& element) {

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

@@ -235,7 +235,7 @@ static inline bool TransformDependsOnReferenceBox(const ComputedStyle& style) {
 }
 
 bool LayoutSVGShape::UpdateLocalTransform() {
-  SVGGraphicsElement* graphics_element = ToSVGGraphicsElement(GetElement());
+  auto* graphics_element = To<SVGGraphicsElement>(GetElement());
   if (graphics_element->HasTransform(SVGElement::kIncludeMotionTransform)) {
     local_transform_.SetTransform(graphics_element->CalculateTransform(
         SVGElement::kIncludeMotionTransform));

third_party/blink/renderer/core/resize_observer/resize_observation.cc

@@ -39,10 +39,9 @@ size_t ResizeObservation::TargetDepth() {
 LayoutSize ResizeObservation::ComputeTargetSize() const {
   if (target_) {
     if (LayoutObject* layout_object = target_->GetLayoutObject()) {
-      auto* svg_element = DynamicTo<SVGElement>(target_.Get());
-      if (svg_element && svg_element->IsSVGGraphicsElement()) {
-        SVGGraphicsElement& svg = ToSVGGraphicsElement(*target_);
-        return LayoutSize(svg.GetBBox().Size());
+      if (auto* svg_graphics_element =
+              DynamicTo<SVGGraphicsElement>(target_.Get())) {
+        return LayoutSize(svg_graphics_element->GetBBox().Size());
       }
       if (layout_object->IsBox())
         return ToLayoutBox(layout_object)->ContentSize();

third_party/blink/renderer/core/svg/svg_graphics_element.h

@@ -91,6 +91,14 @@ inline bool IsSVGGraphicsElement(const SVGElement& element) {
   return element.IsSVGGraphicsElement();
 }
 
+template <>
+struct DowncastTraits<SVGGraphicsElement> {
+  static bool AllowFrom(const Node& node) {
+    auto* svg_element = DynamicTo<SVGElement>(node);
+    return svg_element && IsSVGGraphicsElement(*svg_element);
+  }
+};
+
 DEFINE_SVGELEMENT_TYPE_CASTS_WITH_FUNCTION(SVGGraphicsElement);
 
 }  // namespace blink

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

@@ -323,7 +323,7 @@ bool SVGSVGElement::CheckIntersectionOrEnclosure(
     return false;
 
   AffineTransform ctm =
-      ToSVGGraphicsElement(element).ComputeCTM(kAncestorScope, this);
+      To<SVGGraphicsElement>(element).ComputeCTM(kAncestorScope, this);
   FloatRect mapped_repaint_rect =
       ctm.MapRect(layout_object->VisualRectInLocalSVGCoordinates());
 

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

@@ -499,23 +499,21 @@ Path SVGUseElement::ToClipPath() const {
 
 SVGGraphicsElement* SVGUseElement::VisibleTargetGraphicsElementForClipping()
     const {
-  auto* element = DynamicTo<SVGElement>(UseShadowRoot().firstChild());
-  if (!element)
-    return nullptr;
-
-  if (!element->IsSVGGraphicsElement())
+  auto* svg_graphics_element =
+      DynamicTo<SVGGraphicsElement>(UseShadowRoot().firstChild());
+  if (!svg_graphics_element)
     return nullptr;
 
   // Spec: "If a <use> element is a child of a clipPath element, it must
   // directly reference <path>, <text> or basic shapes elements. Indirect
   // references are an error and the clipPath element must be ignored."
   // https://drafts.fxtf.org/css-masking/#the-clip-path
-  if (!IsDirectReference(*element)) {
+  if (!IsDirectReference(*svg_graphics_element)) {
     // Spec: Indirect references are an error (14.3.5)
     return nullptr;
   }
 
-  return &ToSVGGraphicsElement(*element);
+  return svg_graphics_element;
 }
 
 void SVGUseElement::AddReferencesToFirstDegreeNestedUseElements(