servo: Merge #13589 - Support SVG element (from splav:SVGElement#12974); r=pcwalton,Ms2ger

<!-- Please describe your changes on the following line: -->
minimal SVG element implementation
---
<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `__` with appropriate data: -->
- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes fix #12974 (github issue number if applicable).

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- [x] There are tests for these changes OR
- [ ] These changes do not require tests because _____

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Source-Repo: https://github.com/servo/servo
Source-Revision: dad3b4785a73aa6ddea5ed50ee4ef01bd4049c8d

servo/components/layout/construct.rs

@@ -22,7 +22,7 @@ use floats::FloatKind;
 use flow::{self, AbsoluteDescendants, IS_ABSOLUTELY_POSITIONED, ImmutableFlowUtils};
 use flow::{CAN_BE_FRAGMENTED, MutableFlowUtils, MutableOwnedFlowUtils};
 use flow_ref::{self, FlowRef};
-use fragment::{CanvasFragmentInfo, ImageFragmentInfo, InlineAbsoluteFragmentInfo};
+use fragment::{CanvasFragmentInfo, ImageFragmentInfo, InlineAbsoluteFragmentInfo, SvgFragmentInfo};
 use fragment::{Fragment, GeneratedContentInfo, IframeFragmentInfo};
 use fragment::{InlineAbsoluteHypotheticalFragmentInfo, TableColumnFragmentInfo};
 use fragment::{InlineBlockFragmentInfo, SpecificFragmentInfo, UnscannedTextFragmentInfo};
@@ -335,6 +335,10 @@ impl<'a, ConcreteThreadSafeLayoutNode: ThreadSafeLayoutNode>
                 let data = node.canvas_data().unwrap();
                 SpecificFragmentInfo::Canvas(box CanvasFragmentInfo::new(node, data, self.style_context()))
             }
+            Some(LayoutNodeType::Element(LayoutElementType::SVGSVGElement)) => {
+                let data = node.svg_data().unwrap();
+                SpecificFragmentInfo::Svg(box SvgFragmentInfo::new(node, data, self.style_context()))
+            }
             _ => {
                 // This includes pseudo-elements.
                 SpecificFragmentInfo::Generic
@@ -1701,7 +1705,8 @@ impl<ConcreteThreadSafeLayoutNode> NodeUtils for ConcreteThreadSafeLayoutNode
             Some(LayoutNodeType::Document) |
             Some(LayoutNodeType::Element(LayoutElementType::HTMLImageElement)) |
             Some(LayoutNodeType::Element(LayoutElementType::HTMLIFrameElement)) |
-            Some(LayoutNodeType::Element(LayoutElementType::HTMLCanvasElement)) => true,
+            Some(LayoutNodeType::Element(LayoutElementType::HTMLCanvasElement)) |
+            Some(LayoutNodeType::Element(LayoutElementType::SVGSVGElement)) => true,
             Some(LayoutNodeType::Element(LayoutElementType::HTMLObjectElement)) => self.has_object_data(),
             Some(LayoutNodeType::Element(_)) => false,
             None => self.get_pseudo_element_type().is_replaced_content(),