Add VectorIconButton functionality to ImageButton.

ash/common/system/chromeos/palette/palette_tray.cc

Index: ash/common/system/chromeos/palette/palette_tray.cc
diff --git a/ash/common/system/chromeos/palette/palette_tray.cc b/ash/common/system/chromeos/palette/palette_tray.cc
index b63ad7e5937d4a3fd8214e5c99ec2b7b26941f0f..609240bf2b868f5527de1333dcda02f7440669f4 100644
--- a/ash/common/system/chromeos/palette/palette_tray.cc
+++ b/ash/common/system/chromeos/palette/palette_tray.cc
@@ -33,6 +33,7 @@
 #include "ui/gfx/color_palette.h"
 #include "ui/gfx/paint_vector_icon.h"
 #include "ui/gfx/vector_icons_public.h"
+#include "ui/views/controls/button/image_button.h"
 #include "ui/views/controls/image_view.h"
 #include "ui/views/controls/label.h"
 #include "ui/views/controls/separator.h"
@@ -72,7 +73,7 @@ bool IsInUserSession() {
              LoginStatus::KIOSK_APP;
 }
 
-class TitleView : public views::View, public views::ButtonListener {
+class TitleView : public views::View, public views::ImageButtonDelegate {
  public:
   explicit TitleView(PaletteTray* palette_tray) : palette_tray_(palette_tray) {
     // TODO(tdanderson|jdufault): Use TriView to handle the layout of the title.
@@ -121,7 +122,7 @@ class TitleView : public views::View, public views::ButtonListener {
   ~TitleView() override {}
 
  private:
-  // views::ButtonListener:
+  // views::ImageButtonDelegate:
   void ButtonPressed(views::Button* sender, const ui::Event& event) override {
     if (sender == settings_button_) {
       palette_tray_->RecordPaletteOptionsUsage(