Add some basic tests for bubble controller

* Tests very basic state / interaction
* Doesn't test how bubbles are integrated with the rest
  of the system...

Test: atest BubbleControllerTest
Bug: 111236845
Change-Id: I05e093dc2b7ea2983e018c316689874b66946726
diff --git a/packages/SystemUI/src/com/android/systemui/bubbles/BubbleController.java b/packages/SystemUI/src/com/android/systemui/bubbles/BubbleController.java
index e868f96..4f5a48f 100644
--- a/packages/SystemUI/src/com/android/systemui/bubbles/BubbleController.java
+++ b/packages/SystemUI/src/com/android/systemui/bubbles/BubbleController.java
@@ -32,6 +32,7 @@
 import android.view.WindowManager;
 import android.widget.FrameLayout;
 
+import com.android.internal.annotations.VisibleForTesting;
 import com.android.systemui.Dependency;
 import com.android.systemui.R;
 import com.android.systemui.statusbar.notification.NotificationData;
@@ -67,7 +68,8 @@
     private Point mDisplaySize;
 
     // Bubbles get added to the status bar view
-    private StatusBarWindowController mStatusBarWindowController;
+    @VisibleForTesting
+    protected StatusBarWindowController mStatusBarWindowController;
 
     // Used for determining view rect for touch interaction
     private Rect mTempRect = new Rect();
@@ -297,6 +299,11 @@
         return mTempRect;
     }
 
+    @VisibleForTesting
+    public BubbleStackView getStackView() {
+        return mStackView;
+    }
+
     // TODO: factor in PIP location / maybe last place user had it
     /**
      * Gets an appropriate starting point to position the bubble stack.