[EditContext] Remove inputMode, inputPanelPolicy, enterKeyHint attributes

The following properties exist on the EditContext IDL but are not in
the spec:
- EditContext.inputMode
- EditContext.inputPanelPolicy
- EditContext.enterKeyHint

All three of these now also exist as global attributes on HTMLElement,
so instead of supporting them on EditContext we can instead have
EditContext use the value on the currently focused element, like
how things already work for normal editable elements.

This way, the author can control the value of these by setting the
attributes on the DOM element being edited rather than through
the EditContext itself.

Bug: 999184
Change-Id: I50150bac20cf7448e28e36501f00a6de717e0680
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4698578
Commit-Queue: Dan Clark <daniec@microsoft.com>
Reviewed-by: Kent Tamura <tkent@chromium.org>
Reviewed-by: Anupam Snigdha <snianu@microsoft.com>
Reviewed-by: Koji Ishii <kojii@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1174392}
diff --git a/editing/edit-context/edit-context-basics.tentative.html b/editing/edit-context/edit-context-basics.tentative.html
index a9d7a3d..27bde6e 100644
--- a/editing/edit-context/edit-context-basics.tentative.html
+++ b/editing/edit-context/edit-context-basics.tentative.html
@@ -14,10 +14,7 @@
       const editContextDict = {
         text: "Hello world",
         selectionStart: 11,
-        selectionEnd: 11,
-        inputMode: "text",
-        inputPanelPolicy: "auto",
-        enterKeyHint: "enter"
+        selectionEnd: 11
       };
       const editContext = new EditContext(editContextDict);
       assert_not_equals(editContext, null);
@@ -25,9 +22,6 @@
       assert_equals(editContext.text, "Hello world");
       assert_equals(editContext.selectionStart, 11);
       assert_equals(editContext.selectionEnd, 11);
-      assert_equals(editContext.inputMode, "text");
-      assert_equals(editContext.inputPanelPolicy, "auto");
-      assert_equals(editContext.enterKeyHint, "enter");
     }, 'Testing EditContext Dictionary Init');
 
     test(function() {