Extract out interface for StatusBarHeader

This will allow side by side experimentation with new headers without
breaking everything accidentally.

Change-Id: I9eb4d310f8927c997b83e65dad301f4ab08f618a
diff --git a/packages/SystemUI/src/com/android/systemui/statusbar/phone/NotificationPanelView.java b/packages/SystemUI/src/com/android/systemui/statusbar/phone/NotificationPanelView.java
index 08353cb..3453652 100644
--- a/packages/SystemUI/src/com/android/systemui/statusbar/phone/NotificationPanelView.java
+++ b/packages/SystemUI/src/com/android/systemui/statusbar/phone/NotificationPanelView.java
@@ -92,7 +92,7 @@
     public static final long DOZE_ANIMATION_DURATION = 700;
 
     private KeyguardAffordanceHelper mAfforanceHelper;
-    private StatusBarHeaderView mHeader;
+    private BaseStatusBarHeader mHeader;
     private KeyguardUserSwitcher mKeyguardUserSwitcher;
     private KeyguardStatusBarView mKeyguardStatusBar;
     private QSContainer mQsContainer;
@@ -232,7 +232,7 @@
     @Override
     protected void onFinishInflate() {
         super.onFinishInflate();
-        mHeader = (StatusBarHeaderView) findViewById(R.id.header);
+        mHeader = (BaseStatusBarHeader) findViewById(R.id.header);
         mHeader.setOnClickListener(this);
         mKeyguardStatusBar = (KeyguardStatusBarView) findViewById(R.id.keyguard_header);
         mKeyguardStatusView = (KeyguardStatusView) findViewById(R.id.keyguard_status_view);