MacViews: Implement Full Keyboard Access.

ash/system/user/button_from_view.cc

Index: ash/system/user/button_from_view.cc
diff --git a/ash/system/user/button_from_view.cc b/ash/system/user/button_from_view.cc
index 13bdbb0dd0cf0d0703b50a8bdfd8297cd2a370dd..bbc6bd16c38b3a46650eedac151f3e5ca5ea50d0 100644
--- a/ash/system/user/button_from_view.cc
+++ b/ash/system/user/button_from_view.cc
@@ -43,7 +43,7 @@ ButtonFromView::ButtonFromView(views::View* content,
   ShowActive();
   // Only make it focusable when we are active/interested in clicks.
   if (listener)
-    SetFocusBehavior(FocusBehavior::ALWAYS);
+    Button::ConfigureDefaultFocus(this);
 }
 
 ButtonFromView::~ButtonFromView() {}