Refactor backdrop that is currently used in the maximized mode.

chrome/browser/chromeos/arc/accessibility/arc_accessibility_helper_bridge_unittest.cc

Index: chrome/browser/chromeos/arc/accessibility/arc_accessibility_helper_bridge_unittest.cc
diff --git a/chrome/browser/chromeos/arc/accessibility/arc_accessibility_helper_bridge_unittest.cc b/chrome/browser/chromeos/arc/accessibility/arc_accessibility_helper_bridge_unittest.cc
index 7ea8c89fc937e5c83cf08b4aae98e5a23320719b..1dcec90d228f4a829cc08d2c09b22f140175cf9a 100644
--- a/chrome/browser/chromeos/arc/accessibility/arc_accessibility_helper_bridge_unittest.cc
+++ b/chrome/browser/chromeos/arc/accessibility/arc_accessibility_helper_bridge_unittest.cc
@@ -40,8 +40,6 @@ class ArcAccessibilityHelperBridgeTest : public testing::Test {
     void AddPostTargetHandler(ui::EventHandler* handler) override {}
     void RemovePostTargetHandler(ui::EventHandler* handler) override {}
     bool IsMaximizeModeWindowManagerEnabled() const override { return false; }
-    bool IsSpokenFeedbackEnabled() const override { return false; }
-    void PlayEarcon(int sound_key) const override {}
 
     DISALLOW_COPY_AND_ASSIGN(FakeWMHelper);
   };