Adding four bezel gestures

ash/accelerators/accelerator_controller.h

Index: ash/accelerators/accelerator_controller.h
diff --git a/ash/accelerators/accelerator_controller.h b/ash/accelerators/accelerator_controller.h
index 1c8193d443f7c32995498f1506e2833ca6c035d6..df474275684fa797136c3b5ad5fbe315a9e0b03a 100644
--- a/ash/accelerators/accelerator_controller.h
+++ b/ash/accelerators/accelerator_controller.h
@@ -77,6 +77,10 @@ class ASH_EXPORT AcceleratorController : public ui::AcceleratorTarget {
     return brightness_control_delegate_.get();
   }
 
+  VolumeControlDelegate* volume_control_delegate() const {
+    return volume_control_delegate_.get();
+  }
+
  private:
   // Initializes the accelerators this class handles as a target.
   void Init();