Handle cases where selection API doesn't apply

The selection API only applies to certain <input> types:

https://html.spec.whatwg.org/multipage/#do-not-apply

This commit ensures that we handle that correctly.

Some notes:

1. TextControl::set_dom_selection_direction now calls
   set_selection_range(), which means that setting selectionDirection will
   now fire a selection event, as it should per the spec.

2. There is a test for the firing of the select event in
   tests/wpt/web-platform-tests/html/semantics/forms/textfieldselection/select-event.html,
   however the test did not run due to this syntax error:

   (pid:26017) "ERROR:script::dom::bindings::error: Error at http://web-platform.test:8000/html/semantics/forms/textfieldselection/select-event.html:50:11 missing = in const declaration"

   This happens due to the us of the "for (const foo of ...)" construct.
   Per https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/for...of
   this should actually work, so it's somewhat unsatisfying to have to
   change the test.

4. If an <input>'s type is unset, it defaults to a text, and the
   selection API applies. Also, if an <input>'s type is set to an
   invalid value, it defaults to a text too. I've expanded the tests
   to account for this second case.

1 files changed, 8 insertions, 4 deletions

diff --git a/components/script/dom/webidls/HTMLInputElement.webidl b/components/script/dom/webidls/HTMLInputElement.webidl
index 29bc4b27737..93a5a7f108b 100644
--- a/components/script/dom/webidls/HTMLInputElement.webidl
+++ b/components/script/dom/webidls/HTMLInputElement.webidl
@@ -90,13 +90,17 @@ interface HTMLInputElement : HTMLElement {
   readonly attribute NodeList labels;
 
   //void select();
-           attribute unsigned long selectionStart;
-           attribute unsigned long selectionEnd;
-           attribute DOMString selectionDirection;
+  [SetterThrows]
+           attribute unsigned long? selectionStart;
+  [SetterThrows]
+           attribute unsigned long? selectionEnd;
+  [SetterThrows]
+           attribute DOMString? selectionDirection;
   //void setRangeText(DOMString replacement);
   //void setRangeText(DOMString replacement, unsigned long start, unsigned long end,
   //                  optional SelectionMode selectionMode = "preserve");
-  void setSelectionRange(unsigned long start, unsigned long end, optional DOMString direction);
+  [Throws]
+           void setSelectionRange(unsigned long start, unsigned long end, optional DOMString direction);
 
   // also has obsolete members