[Textfield] Consider select all status for select all context menu

ui/views/controls/textfield/textfield.cc

Index: ui/views/controls/textfield/textfield.cc
diff --git a/ui/views/controls/textfield/textfield.cc b/ui/views/controls/textfield/textfield.cc
index 1586362197bbeeefe7910675eb0c4747e5441b76..3518d9db42e7752d1f6b30305038b94c7a40bbab 100644
--- a/ui/views/controls/textfield/textfield.cc
+++ b/ui/views/controls/textfield/textfield.cc
@@ -353,6 +353,10 @@ void Textfield::SelectAll(bool reversed) {
   UpdateAfterChange(false, true);
 }
 
+bool Textfield::IsAllSelected() const {
+  return !text().empty() && GetSelectedText().length() == text().length();

[Peter Kasting, 2017/04/20 00:08:30]

It seems like it would be more efficient to see if GetSelectedRange() covers the
whole text range.  That wouldn't result in copying the text string just to check
its length.

[simonhong, 2017/04/20 13:11:51]

Done.

+}
+
 void Textfield::SelectWordAt(const gfx::Point& point) {
   model_->MoveCursorTo(point, false);
   model_->SelectWord();
@@ -1546,7 +1550,7 @@ bool Textfield::IsTextEditCommandEnabled(ui::TextEditCommand command) const {
           ui::CLIPBOARD_TYPE_COPY_PASTE, &result);
       return editable && !result.empty();
     case ui::TextEditCommand::SELECT_ALL:
-      return !text().empty();
+      return !IsAllSelected();
     case ui::TextEditCommand::TRANSPOSE:
       return editable && !model_->HasSelection() &&
              !model_->HasCompositionText();