Bug 1518442 - Part 2: Implement Event-based form participation; r=smaug,edgar

For Event-based form participation specification PR:
https://github.com/whatwg/html/pull/4239

Differential Revision: https://phabricator.services.mozilla.com/D43986

dom/html/HTMLFormElement.h

@@ -9,7 +9,6 @@
 
 #include "mozilla/AsyncEventDispatcher.h"
 #include "mozilla/Attributes.h"
-#include "mozilla/dom/HTMLFormSubmission.h"
 #include "nsAutoPtr.h"
 #include "nsCOMPtr.h"
 #include "nsIForm.h"
@@ -33,6 +32,7 @@ class EventChainPreVisitor;
 namespace dom {
 class HTMLFormControlsCollection;
 class HTMLImageElement;
+class FormData;
 
 class HTMLFormElement final : public nsGenericHTMLElement,
                               public nsIWebProgressListener,
@@ -277,12 +277,13 @@ class HTMLFormElement final : public nsGenericHTMLElement,
   bool SubmissionCanProceed(Element* aSubmitter);
 
   /**
-   * Walk over the form elements and call SubmitNamesValues() on them to get
-   * their data pumped into the FormSubmitter.
+   * Contruct the entry list to get their data pumped into the FormData and
+   * fire a `formdata` event with the entry list in formData attribute.
+   * <https://html.spec.whatwg.org/multipage/form-control-infrastructure.html#constructing-form-data-set>
    *
-   * @param aFormSubmission the form submission object
+   * @param aFormData the form data object
    */
-  nsresult WalkFormElements(HTMLFormSubmission* aFormSubmission);
+  nsresult ConstructEntryList(FormData* aFormData);
 
   /**
    * Whether the submission of this form has been ever prevented because of
@@ -611,8 +612,11 @@ class HTMLFormElement final : public nsGenericHTMLElement,
    * being invalid.
    */
   bool mEverTriedInvalidSubmit;
+  /** Whether we are constructing entry list */
+  bool mIsConstructingEntryList;
 
  private:
+  NotNull<const Encoding*> GetSubmitEncoding();
   ~HTMLFormElement();
 };