Move views::Accelerator to ui in order to use it from aura code.

views/controls/button/text_button.cc

Index: views/controls/button/text_button.cc
diff --git a/views/controls/button/text_button.cc b/views/controls/button/text_button.cc
index 0b138cd24c536b69dceb9855dc4bde87c31d00cd..0c5b9ccccb907e4a67e3edd6f9d72cb7ece9b17a 100644
--- a/views/controls/button/text_button.cc
+++ b/views/controls/button/text_button.cc
@@ -304,9 +304,9 @@ void TextButtonBase::SetIsDefault(bool is_default) {
     return;
   is_default_ = is_default;
   if (is_default_)
-    AddAccelerator(Accelerator(ui::VKEY_RETURN, false, false, false));
+    AddAccelerator(ui::Accelerator(ui::VKEY_RETURN, false, false, false));
   else
-    RemoveAccelerator(Accelerator(ui::VKEY_RETURN, false, false, false));
+    RemoveAccelerator(ui::Accelerator(ui::VKEY_RETURN, false, false, false));
   SchedulePaint();
 }