[FIX] web_editor: inline editor should not devore focus

The FieldTextHtmlSimple widget would focus on itself when changing its
value not by direct user interaction. But if this change was coming
from next/previous record, or an onchange that was breaking the
"autofocus" heuristic for field in Odoo.

With this commit:

- the autofocus heuristic is kept,

- if focused, selection is set at the end if it is possible on the
  browser, else (old internet explorer and not visible field) the
  selection is at the beginning.

opw-660486

addons/web_editor/static/src/js/backend.js

@@ -103,17 +103,23 @@ var FieldTextHtmlSimple = widget.extend({
         return value;
     },
     focus: function() {
-        var input = !this.get("effective_readonly") && this.$textarea;
-        return input ? input.focus() : false;
+        if (this.get("effective_readonly")) {
+            return false;
+        }
+        // on IE an error may occur when creating range on not displayed element
+        try {
+            return this.$content.focusInEnd();
+        } catch (e) {
+            return this.$content.focus();
+        };
     },
     render_value: function() {
         var value = this.get('value');
         this.$textarea.val(value || '');
         this.$content.html(this.text_to_html(value));
-        // on ie an error may occur when creating range on not displayed element
-        try {
-            this.$content.focusInEnd();
-        } catch (e) {}
+        if (this.$content.is(document.activeElement)) {
+            this.focus();
+        }
         var history = this.$content.data('NoteHistory');
         if (history && history.recordUndo()) {
             this.$('.note-toolbar').find('button[data-event="undo"]').attr('disabled', false);