Refactor MdFocusRing to make it easier to reuse on other controls.

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 4642d23fc89a89633cc84ff72fbb5011959a7b9d..7c7b03534634c075e20a209397b5897961b0bbcf 100644
--- a/ui/views/controls/textfield/textfield.cc
+++ b/ui/views/controls/textfield/textfield.cc
@@ -33,6 +33,7 @@
 #include "ui/native_theme/native_theme.h"
 #include "ui/strings/grit/ui_strings.h"
 #include "ui/views/background.h"
+#include "ui/views/controls/focus_ring.h"
 #include "ui/views/controls/focusable_border.h"
 #include "ui/views/controls/label.h"
 #include "ui/views/controls/menu/menu_runner.h"
@@ -990,6 +991,8 @@ void Textfield::OnFocus() {
     StartBlinkingCursor();
   View::OnFocus();
   SchedulePaint();
+  if (ui::MaterialDesignController::IsSecondaryUiMaterial())
+    FocusRing::Install(this);
 }
 
 void Textfield::OnBlur() {
@@ -1007,6 +1010,8 @@ void Textfield::OnBlur() {
 
   // Border typically draws focus indicator.
   SchedulePaint();
+  if (ui::MaterialDesignController::IsSecondaryUiMaterial())
+    FocusRing::Uninstall(this);
 }
 
 gfx::Point Textfield::GetKeyboardContextMenuLocation() {