Bug 1316661 part 5. Eliminate IsCallerChrome caller in HTMLTextareaElement. r=smaug

The WebIDL caller of SetUserInput is [ChromeOnly] and the other callers are all C++ code that should be able to set the value.

dom/html/HTMLTextAreaElement.cpp

@@ -363,9 +363,6 @@ HTMLTextAreaElement::SetValue(const nsAString& aValue)
 NS_IMETHODIMP 
 HTMLTextAreaElement::SetUserInput(const nsAString& aValue)
 {
-  if (!nsContentUtils::IsCallerChrome()) {
-    return NS_ERROR_DOM_SECURITY_ERR;
-  }
   return SetValueInternal(aValue, nsTextEditorState::eSetValue_BySetUserInput);
 }