Initial IndexedDB Support (#33044)

Adds indexeddb support to servo. At the moment heed is being used as the
backend, although this can be swapped out by implementing `KvsEngine`.
This PR adds a thread + a thread pool for Indexeddb related operations.
Also `database_access_task_source` is added for Indexeddb related
operations.

This is a partial rewrite of #25214. (Reopened due to branching issue)

Fixes #6963

---------

Signed-off-by: Ashwin Naren <arihant2math@gmail.com>
Signed-off-by: Josh Matthews <josh@joshmatthews.net>
Co-authored-by: Rasmus Viitanen <rasviitanen@gmail.com>
Co-authored-by: Josh Matthews <josh@joshmatthews.net>

components/script/dom/idbversionchangeevent.rs

@@ -0,0 +1,117 @@
+/* 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 dom_struct::dom_struct;
+use stylo_atoms::Atom;
+
+use crate::dom::bindings::codegen::Bindings::EventBinding::EventMethods;
+use crate::dom::bindings::codegen::Bindings::IDBVersionChangeEventBinding::{
+    IDBVersionChangeEventInit, IDBVersionChangeEventMethods,
+};
+use crate::dom::bindings::import::module::HandleObject;
+use crate::dom::bindings::inheritance::Castable;
+use crate::dom::bindings::reflector::{DomGlobal, reflect_dom_object};
+use crate::dom::bindings::root::DomRoot;
+use crate::dom::bindings::str::DOMString;
+use crate::dom::event::{Event, EventBubbles, EventCancelable};
+use crate::dom::globalscope::GlobalScope;
+use crate::dom::window::Window;
+use crate::script_runtime::CanGc;
+
+#[dom_struct]
+pub(crate) struct IDBVersionChangeEvent {
+    event: Event,
+    old_version: u64,
+    new_version: Option<u64>,
+}
+
+impl IDBVersionChangeEvent {
+    pub fn new_inherited(old_version: u64, new_version: Option<u64>) -> IDBVersionChangeEvent {
+        IDBVersionChangeEvent {
+            event: Event::new_inherited(),
+            old_version,
+            new_version,
+        }
+    }
+
+    pub fn new(
+        global: &GlobalScope,
+        type_: Atom,
+        bubbles: EventBubbles,
+        cancelable: EventCancelable,
+        old_version: u64,
+        new_version: Option<u64>,
+        can_gc: CanGc,
+    ) -> DomRoot<IDBVersionChangeEvent> {
+        Self::new_with_proto(
+            global,
+            type_,
+            bool::from(bubbles),
+            bool::from(cancelable),
+            old_version,
+            new_version,
+            can_gc,
+        )
+    }
+
+    fn new_with_proto(
+        global: &GlobalScope,
+        type_: Atom,
+        bubbles: bool,
+        cancelable: bool,
+        old_version: u64,
+        new_version: Option<u64>,
+        can_gc: CanGc,
+    ) -> DomRoot<Self> {
+        let ev = reflect_dom_object(
+            Box::new(IDBVersionChangeEvent::new_inherited(
+                old_version,
+                new_version,
+            )),
+            global,
+            can_gc,
+        );
+        {
+            let event = ev.upcast::<Event>();
+            event.init_event(type_, bubbles, cancelable);
+        }
+        ev
+    }
+}
+
+impl IDBVersionChangeEventMethods<crate::DomTypeHolder> for IDBVersionChangeEvent {
+    /// <https://w3c.github.io/IndexedDB/#dom-idbversionchangeevent-idbversionchangeevent>
+    fn Constructor(
+        window: &Window,
+        _proto: Option<HandleObject>,
+        can_gc: CanGc,
+        type_: DOMString,
+        init: &IDBVersionChangeEventInit,
+    ) -> DomRoot<Self> {
+        Self::new_with_proto(
+            &window.global(),
+            Atom::from(type_),
+            init.parent.bubbles,
+            init.parent.cancelable,
+            init.oldVersion,
+            init.newVersion,
+            can_gc,
+        )
+    }
+
+    // https://www.w3.org/TR/IndexedDB-2/#dom-idbversionchangeevent-oldversion
+    fn OldVersion(&self) -> u64 {
+        self.old_version
+    }
+
+    // https://www.w3.org/TR/IndexedDB-2/#dom-idbversionchangeevent-newversion
+    fn GetNewVersion(&self) -> Option<u64> {
+        self.new_version
+    }
+
+    // https://dom.spec.whatwg.org/#dom-event-istrusted
+    fn IsTrusted(&self) -> bool {
+        self.event.IsTrusted()
+    }
+}