13 files changed, 89 insertions, 24 deletions
diff --git a/components/script/dom/element.rs b/components/script/dom/element.rs
index baccc4e65aa..6f6f33f56a8 100644
--- a/components/script/dom/element.rs
+++ b/components/script/dom/element.rs
@@ -2449,8 +2449,6 @@ impl ElementMethods for Element {
 
     /// <https://w3c.github.io/DOM-Parsing/#widl-Element-innerHTML>
     fn SetInnerHTML(&self, value: DOMString) -> ErrorResult {
-        // Step 1.
-        let frag = self.parse_fragment(value)?;
         // Step 2.
         // https://github.com/w3c/DOM-Parsing/issues/1
         let target = if let Some(template) = self.downcast::<HTMLTemplateElement>() {
@@ -2458,6 +2456,23 @@ impl ElementMethods for Element {
         } else {
             DomRoot::from_ref(self.upcast())
         };
+
+        // Fast path for when the value is small, doesn't contain any markup and doesn't require
+        // extra work to set innerHTML.
+        if !self.node.has_weird_parser_insertion_mode() &&
+            value.len() < 100 &&
+            !value
+                .as_bytes()
+                .iter()
+                .any(|c| matches!(*c, b'&' | b'\0' | b'<' | b'\r'))
+        {
+            Node::SetTextContent(&target, Some(value));
+            return Ok(());
+        }
+
+        // Step 1.
+        let frag = self.parse_fragment(value)?;
+
         Node::replace_all(Some(frag.upcast()), &target);
         Ok(())
     }
diff --git a/components/script/dom/htmlframesetelement.rs b/components/script/dom/htmlframesetelement.rs
index 2c7260ee2c1..dc071b47074 100644
--- a/components/script/dom/htmlframesetelement.rs
+++ b/components/script/dom/htmlframesetelement.rs
@@ -4,6 +4,7 @@
 
 use crate::dom::bindings::codegen::Bindings::HTMLFrameSetElementBinding::HTMLFrameSetElementMethods;
 use crate::dom::bindings::codegen::Bindings::WindowBinding::WindowMethods;
+use crate::dom::bindings::inheritance::Castable;
 use crate::dom::bindings::root::DomRoot;
 use crate::dom::document::Document;
 use crate::dom::htmlelement::HTMLElement;
@@ -33,12 +34,14 @@ impl HTMLFrameSetElement {
         prefix: Option<Prefix>,
         document: &Document,
     ) -> DomRoot<HTMLFrameSetElement> {
-        Node::reflect_node(
+        let n = Node::reflect_node(
             Box::new(HTMLFrameSetElement::new_inherited(
                 local_name, prefix, document,
             )),
             document,
-        )
+        );
+        n.upcast::<Node>().set_weird_parser_insertion_mode();
+        n
     }
 }
 
diff --git a/components/script/dom/htmlheadelement.rs b/components/script/dom/htmlheadelement.rs
index efa0bc7d515..1bd6e5e1148 100644
--- a/components/script/dom/htmlheadelement.rs
+++ b/components/script/dom/htmlheadelement.rs
@@ -37,10 +37,13 @@ impl HTMLHeadElement {
         prefix: Option<Prefix>,
         document: &Document,
     ) -> DomRoot<HTMLHeadElement> {
-        Node::reflect_node(
+        let n = Node::reflect_node(
             Box::new(HTMLHeadElement::new_inherited(local_name, prefix, document)),
             document,
-        )
+        );
+
+        n.upcast::<Node>().set_weird_parser_insertion_mode();
+        n
     }
 
     /// <https://html.spec.whatwg.org/multipage/#meta-referrer>
diff --git a/components/script/dom/htmlhtmlelement.rs b/components/script/dom/htmlhtmlelement.rs
index 05b34dec3dc..da77d3464d9 100644
--- a/components/script/dom/htmlhtmlelement.rs
+++ b/components/script/dom/htmlhtmlelement.rs
@@ -2,6 +2,7 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
+use crate::dom::bindings::inheritance::Castable;
 use crate::dom::bindings::root::DomRoot;
 use crate::dom::document::Document;
 use crate::dom::htmlelement::HTMLElement;
@@ -32,9 +33,12 @@ impl HTMLHtmlElement {
         prefix: Option<Prefix>,
         document: &Document,
     ) -> DomRoot<HTMLHtmlElement> {
-        Node::reflect_node(
+        let n = Node::reflect_node(
             Box::new(HTMLHtmlElement::new_inherited(localName, prefix, document)),
             document,
-        )
+        );
+
+        n.upcast::<Node>().set_weird_parser_insertion_mode();
+        n
     }
 }
diff --git a/components/script/dom/htmlselectelement.rs b/components/script/dom/htmlselectelement.rs
index caca2fddfc2..9d36413e4b5 100755
--- a/components/script/dom/htmlselectelement.rs
+++ b/components/script/dom/htmlselectelement.rs
@@ -93,12 +93,15 @@ impl HTMLSelectElement {
         prefix: Option<Prefix>,
         document: &Document,
     ) -> DomRoot<HTMLSelectElement> {
-        Node::reflect_node(
+        let n = Node::reflect_node(
             Box::new(HTMLSelectElement::new_inherited(
                 local_name, prefix, document,
             )),
             document,
-        )
+        );
+
+        n.upcast::<Node>().set_weird_parser_insertion_mode();
+        n
     }
 
     // https://html.spec.whatwg.org/multipage/#concept-select-option-list
diff --git a/components/script/dom/htmltablecaptionelement.rs b/components/script/dom/htmltablecaptionelement.rs
index e6ff3da673e..b89b647691e 100644
--- a/components/script/dom/htmltablecaptionelement.rs
+++ b/components/script/dom/htmltablecaptionelement.rs
@@ -2,6 +2,7 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
+use crate::dom::bindings::inheritance::Castable;
 use crate::dom::bindings::root::DomRoot;
 use crate::dom::document::Document;
 use crate::dom::htmlelement::HTMLElement;
@@ -31,11 +32,14 @@ impl HTMLTableCaptionElement {
         prefix: Option<Prefix>,
         document: &Document,
     ) -> DomRoot<HTMLTableCaptionElement> {
-        Node::reflect_node(
+        let n = Node::reflect_node(
             Box::new(HTMLTableCaptionElement::new_inherited(
                 local_name, prefix, document,
             )),
             document,
-        )
+        );
+
+        n.upcast::<Node>().set_weird_parser_insertion_mode();
+        n
     }
 }
diff --git a/components/script/dom/htmltablecellelement.rs b/components/script/dom/htmltablecellelement.rs
index 81e9dafb1cc..75a2140a090 100644
--- a/components/script/dom/htmltablecellelement.rs
+++ b/components/script/dom/htmltablecellelement.rs
@@ -45,12 +45,15 @@ impl HTMLTableCellElement {
         prefix: Option<Prefix>,
         document: &Document,
     ) -> DomRoot<HTMLTableCellElement> {
-        Node::reflect_node(
+        let n = Node::reflect_node(
             Box::new(HTMLTableCellElement::new_inherited(
                 local_name, prefix, document,
             )),
             document,
-        )
+        );
+
+        n.upcast::<Node>().set_weird_parser_insertion_mode();
+        n
     }
 }
 
diff --git a/components/script/dom/htmltablecolelement.rs b/components/script/dom/htmltablecolelement.rs
index 7dcd27d953d..86382e1c2cb 100644
--- a/components/script/dom/htmltablecolelement.rs
+++ b/components/script/dom/htmltablecolelement.rs
@@ -2,6 +2,7 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
+use crate::dom::bindings::inheritance::Castable;
 use crate::dom::bindings::root::DomRoot;
 use crate::dom::document::Document;
 use crate::dom::htmlelement::HTMLElement;
@@ -31,11 +32,14 @@ impl HTMLTableColElement {
         prefix: Option<Prefix>,
         document: &Document,
     ) -> DomRoot<HTMLTableColElement> {
-        Node::reflect_node(
+        let n = Node::reflect_node(
             Box::new(HTMLTableColElement::new_inherited(
                 local_name, prefix, document,
             )),
             document,
-        )
+        );
+
+        n.upcast::<Node>().set_weird_parser_insertion_mode();
+        n
     }
 }
diff --git a/components/script/dom/htmltableelement.rs b/components/script/dom/htmltableelement.rs
index f42e72b5247..2fa44f3ad37 100644
--- a/components/script/dom/htmltableelement.rs
+++ b/components/script/dom/htmltableelement.rs
@@ -70,12 +70,15 @@ impl HTMLTableElement {
         prefix: Option<Prefix>,
         document: &Document,
     ) -> DomRoot<HTMLTableElement> {
-        Node::reflect_node(
+        let n = Node::reflect_node(
             Box::new(HTMLTableElement::new_inherited(
                 local_name, prefix, document,
             )),
             document,
-        )
+        );
+
+        n.upcast::<Node>().set_weird_parser_insertion_mode();
+        n
     }
 
     pub fn get_border(&self) -> Option<u32> {
diff --git a/components/script/dom/htmltablerowelement.rs b/components/script/dom/htmltablerowelement.rs
index 1bece55857b..5da05be4019 100644
--- a/components/script/dom/htmltablerowelement.rs
+++ b/components/script/dom/htmltablerowelement.rs
@@ -57,12 +57,15 @@ impl HTMLTableRowElement {
         prefix: Option<Prefix>,
         document: &Document,
     ) -> DomRoot<HTMLTableRowElement> {
-        Node::reflect_node(
+        let n = Node::reflect_node(
             Box::new(HTMLTableRowElement::new_inherited(
                 local_name, prefix, document,
             )),
             document,
-        )
+        );
+
+        n.upcast::<Node>().set_weird_parser_insertion_mode();
+        n
     }
 
     /// Determine the index for this `HTMLTableRowElement` within the given
diff --git a/components/script/dom/htmltablesectionelement.rs b/components/script/dom/htmltablesectionelement.rs
index fa0f3b93ab5..5787546f2be 100644
--- a/components/script/dom/htmltablesectionelement.rs
+++ b/components/script/dom/htmltablesectionelement.rs
@@ -42,12 +42,15 @@ impl HTMLTableSectionElement {
         prefix: Option<Prefix>,
         document: &Document,
     ) -> DomRoot<HTMLTableSectionElement> {
-        Node::reflect_node(
+        let n = Node::reflect_node(
             Box::new(HTMLTableSectionElement::new_inherited(
                 local_name, prefix, document,
             )),
             document,
-        )
+        );
+
+        n.upcast::<Node>().set_weird_parser_insertion_mode();
+        n
     }
 }
 
diff --git a/components/script/dom/htmltemplateelement.rs b/components/script/dom/htmltemplateelement.rs
index 87f2063f5e3..673f6e0c98a 100644
--- a/components/script/dom/htmltemplateelement.rs
+++ b/components/script/dom/htmltemplateelement.rs
@@ -41,12 +41,15 @@ impl HTMLTemplateElement {
         prefix: Option<Prefix>,
         document: &Document,
     ) -> DomRoot<HTMLTemplateElement> {
-        Node::reflect_node(
+        let n = Node::reflect_node(
             Box::new(HTMLTemplateElement::new_inherited(
                 local_name, prefix, document,
             )),
             document,
-        )
+        );
+
+        n.upcast::<Node>().set_weird_parser_insertion_mode();
+        n
     }
 }
 
diff --git a/components/script/dom/node.rs b/components/script/dom/node.rs
index 4579890a03e..503cc589b50 100644
--- a/components/script/dom/node.rs
+++ b/components/script/dom/node.rs
@@ -196,6 +196,10 @@ bitflags! {
 
         /// Specifies whether this node's shadow-including root is a document.
         const IS_CONNECTED = 1 << 10;
+
+        /// Whether this node has a weird parser insertion mode. i.e whether setting innerHTML
+        /// needs extra work or not
+        const HAS_WEIRD_PARSER_INSERTION_MODE = 1 << 11;
     }
 }
 
@@ -554,6 +558,16 @@ impl Node {
         self.flags.get().contains(NodeFlags::IS_IN_SHADOW_TREE)
     }
 
+    pub fn has_weird_parser_insertion_mode(&self) -> bool {
+        self.flags
+            .get()
+            .contains(NodeFlags::HAS_WEIRD_PARSER_INSERTION_MODE)
+    }
+
+    pub fn set_weird_parser_insertion_mode(&self) {
+        self.set_flag(NodeFlags::HAS_WEIRD_PARSER_INSERTION_MODE, true)
+    }
+
     pub fn is_connected(&self) -> bool {
         self.flags.get().contains(NodeFlags::IS_CONNECTED)
     }