Add text field change handling for autofill preview in textarea element.

Source/web/WebTextAreaElement.cpp

Index: Source/web/WebTextAreaElement.cpp
diff --git a/Source/web/WebTextAreaElement.cpp b/Source/web/WebTextAreaElement.cpp
index c4ecd8b95e8db4b88c02170538f32e9b435ce029..e55410e1f7cb41cb3c1b4efb86a36d5f00552763 100644
--- a/Source/web/WebTextAreaElement.cpp
+++ b/Source/web/WebTextAreaElement.cpp
@@ -60,6 +60,11 @@ WebString WebTextAreaElement::suggestedValue() const
     return constUnwrap<HTMLTextAreaElement>()->suggestedValue();
 }
 
+void WebTextAreaElement::setSelectionRange(int start, int end)
+{
+    unwrap<HTMLTextAreaElement>()->setSelectionRange(start, end);
+}
+
 WebTextAreaElement::WebTextAreaElement(const PassRefPtr<HTMLTextAreaElement>& element)
     : WebFormControlElement(element)
 {