Bug 1773070 - Unify Gecko and Servo EventState/ElementState bits. r=smaug

Add a dom/base/rust crate called just "dom" where we can share these.

Most of the changes are automatic:

  s/mozilla::EventStates/mozilla::dom::ElementState/
  s/EventStates/ElementState/
  s/NS_EVENT_STATE_/ElementState::/
  s/NS_DOCUMENT_STATE_/DocumentState::/

And so on. This requires a new cbindgen version to avoid ugly casts for
large shifts.

Differential Revision: https://phabricator.services.mozilla.com/D148537

dom/html/HTMLObjectElement.cpp

@@ -4,7 +4,6 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
-#include "mozilla/EventStates.h"
 #include "mozilla/dom/BindContext.h"
 #include "mozilla/dom/Document.h"
 #include "mozilla/dom/HTMLObjectElement.h"
@@ -38,7 +37,7 @@ HTMLObjectElement::HTMLObjectElement(
   SetBarredFromConstraintValidation(true);
 
   // By default we're in the loading state
-  AddStatesSilently(NS_EVENT_STATE_LOADING);
+  AddStatesSilently(ElementState::LOADING);
 }
 
 HTMLObjectElement::~HTMLObjectElement() {
@@ -284,7 +283,7 @@ void HTMLObjectElement::StartObjectLoad(bool aNotify, bool aForce) {
   SetIsNetworkCreated(false);
 }
 
-EventStates HTMLObjectElement::IntrinsicState() const {
+ElementState HTMLObjectElement::IntrinsicState() const {
   return nsGenericHTMLFormControlElement::IntrinsicState() | ObjectState();
 }