Bug 230307. When cloning a <textarea>, preserve the current value jus…

…t like we do for <input>. r=ehsan

The web platform test is just lifted wholesale from
<web-platform-tests/wpt#3734>.

UltraBlame original commit: 9169054bf50447beb0a7793b1c289763ec12ba79

dom/html/HTMLTextAreaElement.cpp

@@ -617,10 +617,169 @@ nsGenericHTMLFormElementWithState
 /
 /
 nsIDOMHTMLTextAreaElement
-NS_IMPL_ELEMENT_CLONE
+nsresult
+HTMLTextAreaElement
+:
+:
+Clone
+(
+mozilla
+:
+:
+dom
+:
+:
+NodeInfo
+*
+aNodeInfo
+nsINode
+*
+*
+aResult
+)
+const
+{
+*
+aResult
+=
+nullptr
+;
+already_AddRefed
+<
+mozilla
+:
+:
+dom
+:
+:
+NodeInfo
+>
+ni
+=
+RefPtr
+<
+mozilla
+:
+:
+dom
+:
+:
+NodeInfo
+>
+(
+aNodeInfo
+)
+.
+forget
+(
+)
+;
+RefPtr
+<
+HTMLTextAreaElement
+>
+it
+=
+new
+HTMLTextAreaElement
 (
+ni
+)
+;
+nsresult
+rv
+=
+const_cast
+<
 HTMLTextAreaElement
+*
+>
+(
+this
 )
+-
+>
+CopyInnerTo
+(
+it
+)
+;
+NS_ENSURE_SUCCESS
+(
+rv
+rv
+)
+;
+if
+(
+mValueChanged
+)
+{
+/
+/
+Set
+our
+value
+on
+the
+clone
+.
+nsAutoString
+value
+;
+GetValueInternal
+(
+value
+true
+)
+;
+/
+/
+SetValueInternal
+handles
+setting
+mValueChanged
+for
+us
+rv
+=
+it
+-
+>
+SetValueInternal
+(
+value
+nsTextEditorState
+:
+:
+eSetValue_Notify
+)
+;
+NS_ENSURE_SUCCESS
+(
+rv
+rv
+)
+;
+}
+it
+-
+>
+mLastValueChangeWasInteractive
+=
+mLastValueChangeWasInteractive
+;
+it
+.
+forget
+(
+aResult
+)
+;
+return
+NS_OK
+;
+}
 /
 /
 nsIConstraintValidation

testing/web-platform/meta/MANIFEST.json

@@ -486667,6 +486667,77 @@ html
 /
 semantics
 /
+forms
+/
+the
+-
+textarea
+-
+element
+/
+cloning
+-
+steps
+.
+html
+"
+:
+[
+{
+"
+path
+"
+:
+"
+html
+/
+semantics
+/
+forms
+/
+the
+-
+textarea
+-
+element
+/
+cloning
+-
+steps
+.
+html
+"
+"
+url
+"
+:
+"
+/
+html
+/
+semantics
+/
+forms
+/
+the
+-
+textarea
+-
+element
+/
+cloning
+-
+steps
+.
+html
+"
+}
+]
+"
+html
+/
+semantics
+/
 scripting
 -
 1