script: Refactors HTMLInputElement.rs into type specific files (#43325)

Refactors HTMLInputElement.rs to split lots of type specific input code
into their own files. These SpecificInputTypes are responsible for their
own shadow trees and also for element specific data such as
FileInputType's filelist.

Testing: Covered by WPTs
Fixes: https://github.com/servo/servo/issues/38263
Fixes: https://github.com/servo/servo/issues/43351

Signed-off-by: Luke Warlow <lwarlow@igalia.com>
Co-authored-by: Oriol Brufau <obrufau@igalia.com>

components/script/dom/html/input_element/text_value_widget.rs

@@ -0,0 +1,82 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * 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 std::cell::Ref;
+
+use js::context::JSContext;
+use script_bindings::codegen::GenericBindings::CharacterDataBinding::CharacterDataMethods;
+use script_bindings::root::Dom;
+use script_bindings::script_runtime::CanGc;
+
+use crate::dom::bindings::cell::DomRefCell;
+use crate::dom::bindings::inheritance::Castable;
+use crate::dom::characterdata::CharacterData;
+use crate::dom::element::Element;
+use crate::dom::htmlinputelement::HTMLInputElement;
+use crate::dom::node::{Node, NodeTraits};
+use crate::dom::text::Text;
+
+#[derive(Default, JSTraceable, MallocSizeOf, PartialEq)]
+#[cfg_attr(crown, crown::unrooted_must_root_lint::must_root)]
+pub(crate) struct TextValueWidget {
+    shadow_tree: DomRefCell<Option<TextValueShadowTree>>,
+}
+
+impl TextValueWidget {
+    /// Get the shadow tree for this [`HTMLInputElement`], if it is created and valid, otherwise
+    /// recreate the shadow tree and return it.
+    fn get_or_create_shadow_tree(
+        &self,
+        cx: &mut JSContext,
+        input: &HTMLInputElement,
+    ) -> Ref<'_, TextValueShadowTree> {
+        {
+            if let Ok(shadow_tree) = Ref::filter_map(self.shadow_tree.borrow(), |shadow_tree| {
+                shadow_tree.as_ref()
+            }) {
+                return shadow_tree;
+            }
+        }
+
+        let element = input.upcast::<Element>();
+        let shadow_root = element
+            .shadow_root()
+            .unwrap_or_else(|| element.attach_ua_shadow_root(cx, true));
+        let shadow_root = shadow_root.upcast();
+        *self.shadow_tree.borrow_mut() = Some(TextValueShadowTree::new(cx, shadow_root));
+        self.get_or_create_shadow_tree(cx, input)
+    }
+
+    pub(crate) fn update_shadow_tree(&self, cx: &mut JSContext, input: &HTMLInputElement) {
+        self.get_or_create_shadow_tree(cx, input).update(input)
+    }
+}
+
+#[derive(Clone, JSTraceable, MallocSizeOf, PartialEq)]
+#[cfg_attr(crown, crown::unrooted_must_root_lint::must_root)]
+struct TextValueShadowTree {
+    value: Dom<Text>,
+}
+
+impl TextValueShadowTree {
+    fn new(cx: &mut JSContext, shadow_root: &Node) -> Self {
+        let value = Text::new(
+            Default::default(),
+            &shadow_root.owner_document(),
+            CanGc::from_cx(cx),
+        );
+        Node::replace_all(cx, Some(value.upcast()), shadow_root);
+        Self {
+            value: value.as_traced(),
+        }
+    }
+
+    fn update(&self, input_element: &HTMLInputElement) {
+        let character_data = self.value.upcast::<CharacterData>();
+        let value = input_element.value_for_shadow_dom();
+        if character_data.Data() != value {
+            character_data.SetData(value);
+        }
+    }
+}