Rearrange top level definitions

Improve consistency. The HTMLBaseElement methods should follow the
HTMLBaseElement type definition, rather than be elsewhere.

Move ValidityState down, after all HTML elements. Its previous location
in the middle was too arbitrary. Many HTML elements use ValidityState.

dom.go

@@ -1852,22 +1852,19 @@ func (e *HTMLAreaElement) Rel() *TokenList {
 type HTMLAudioElement struct{ *HTMLMediaElement }
 
 type HTMLBRElement struct{ *BasicHTMLElement }
+
 type HTMLBaseElement struct{ *BasicHTMLElement }
-type HTMLBodyElement struct{ *BasicHTMLElement }
 
-type ValidityState struct {
-	*js.Object
-	CustomError     bool `js:"customError"`
-	PatternMismatch bool `js:"patternMismatch"`
-	RangeOverflow   bool `js:"rangeOverflow"`
-	RangeUnderflow  bool `js:"rangeUnderflow"`
-	StepMismatch    bool `js:"stepMismatch"`
-	TooLong         bool `js:"tooLong"`
-	TypeMismatch    bool `js:"typeMismatch"`
-	Valid           bool `js:"valid"`
-	ValueMissing    bool `js:"valueMissing"`
+func (e *HTMLBaseElement) Href() string {
+	return e.Get("href").String()
+}
+
+func (e *HTMLBaseElement) Target() string {
+	return e.Get("target").String()
 }
 
+type HTMLBodyElement struct{ *BasicHTMLElement }
+
 type HTMLButtonElement struct {
 	*BasicHTMLElement
 	AutoFocus         bool   `js:"autofocus"`
@@ -3029,12 +3026,17 @@ type HTMLUnknownElement struct{ *BasicHTMLElement }
 
 type HTMLVideoElement struct{ *HTMLMediaElement }
 
-func (e *HTMLBaseElement) Href() string {
-	return e.Get("href").String()
-}
-
-func (e *HTMLBaseElement) Target() string {
-	return e.Get("target").String()
+type ValidityState struct {
+	*js.Object
+	CustomError     bool `js:"customError"`
+	PatternMismatch bool `js:"patternMismatch"`
+	RangeOverflow   bool `js:"rangeOverflow"`
+	RangeUnderflow  bool `js:"rangeUnderflow"`
+	StepMismatch    bool `js:"stepMismatch"`
+	TooLong         bool `js:"tooLong"`
+	TypeMismatch    bool `js:"typeMismatch"`
+	Valid           bool `js:"valid"`
+	ValueMissing    bool `js:"valueMissing"`
 }
 
 type CSSStyleDeclaration struct{ *js.Object }