sysui: refactor for extensibility.

1. Refactored container height calculation out of updateBottom of QSContainer;

2. Added a method in QSContainer to return min expansion height.

Bug: 27929808
Change-Id: I5a6d04ffb225bccfc56fa5f4ab98d330ed763a8c
(cherry picked from commit 9e874950195d6b76a64e28c236e8d109d551281f)
diff --git a/packages/SystemUI/src/com/android/systemui/qs/QSContainer.java b/packages/SystemUI/src/com/android/systemui/qs/QSContainer.java
index 0af5fa6..e3a4909 100644
--- a/packages/SystemUI/src/com/android/systemui/qs/QSContainer.java
+++ b/packages/SystemUI/src/com/android/systemui/qs/QSContainer.java
@@ -47,10 +47,10 @@
     private final Rect mQsBounds = new Rect();
 
     private int mHeightOverride = -1;
-    private QSPanel mQSPanel;
+    protected QSPanel mQSPanel;
     private QSDetail mQSDetail;
     protected BaseStatusBarHeader mHeader;
-    private float mQsExpansion;
+    protected float mQsExpansion;
     private boolean mQsExpanded;
     private boolean mHeaderAnimating;
     private boolean mKeyguardShowing;
@@ -162,14 +162,18 @@
     }
 
     private void updateBottom() {
-        int heightOverride = mHeightOverride != -1 ? mHeightOverride : getMeasuredHeight();
-        int height = mQSCustomizer.isCustomizing() ? mQSCustomizer.getHeight()
-                : (int) (mQsExpansion * (heightOverride - mHeader.getCollapsedHeight()))
-                + mHeader.getCollapsedHeight();
+        int height = calculateContainerHeight();
         setBottom(getTop() + height);
         mQSDetail.setBottom(getTop() + height);
     }
 
+    protected int calculateContainerHeight() {
+        int heightOverride = mHeightOverride != -1 ? mHeightOverride : getMeasuredHeight();
+        return mQSCustomizer.isCustomizing() ? mQSCustomizer.getHeight()
+                : (int) (mQsExpansion * (heightOverride - mHeader.getCollapsedHeight()))
+                + mHeader.getCollapsedHeight();
+    }
+
     private void updateQsState() {
         boolean expandVisually = mQsExpanded || mStackScrollerOverscrolling || mHeaderAnimating;
         mQSPanel.setExpanded(mQsExpanded);
@@ -302,4 +306,8 @@
             updateQsState();
         }
     };
+
+    public int getQsMinExpansionHeight() {
+        return mHeader.getHeight();
+    }
 }
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 45e94f7..62c0fa9 100644
--- a/packages/SystemUI/src/com/android/systemui/statusbar/phone/NotificationPanelView.java
+++ b/packages/SystemUI/src/com/android/systemui/statusbar/phone/NotificationPanelView.java
@@ -306,7 +306,7 @@
 
         // Calculate quick setting heights.
         int oldMaxHeight = mQsMaxExpansionHeight;
-        mQsMinExpansionHeight = mKeyguardShowing ? 0 : mQsContainer.getHeader().getHeight();
+        mQsMinExpansionHeight = mKeyguardShowing ? 0 : mQsContainer.getQsMinExpansionHeight();
         mQsMaxExpansionHeight = mQsContainer.getDesiredHeight();
         positionClockAndNotifications();
         if (mQsExpanded && mQsFullyExpanded) {
diff --git a/packages/SystemUI/src/com/android/systemui/statusbar/stack/NotificationStackScrollLayout.java b/packages/SystemUI/src/com/android/systemui/statusbar/stack/NotificationStackScrollLayout.java
index 0e3ec19..7c5cdfb 100644
--- a/packages/SystemUI/src/com/android/systemui/statusbar/stack/NotificationStackScrollLayout.java
+++ b/packages/SystemUI/src/com/android/systemui/statusbar/stack/NotificationStackScrollLayout.java
@@ -299,7 +299,7 @@
             setDimAmount((Float) animation.getAnimatedValue());
         }
     };
-    private ViewGroup mQsContainer;
+    protected ViewGroup mQsContainer;
     private boolean mContinuousShadowUpdate;
     private ViewTreeObserver.OnPreDrawListener mShadowUpdater
             = new ViewTreeObserver.OnPreDrawListener() {