Add a triangluar pointer to indicate the currently expanded bubble

Introduces BubbleExpandedViewContainer to wrap the currently expanded
view and render the triangle
   * This view should also handle rendering the header
   * ActivityView will live here too eventually maybe

Test: visual - enable bubbles, open a bubble, note the pointer
Bug: 111236845
Change-Id: I49569a0355eab29c9f1b6bb9abe1cd2d10b9b27b
diff --git a/packages/SystemUI/res/layout/bubble_expanded_view.xml b/packages/SystemUI/res/layout/bubble_expanded_view.xml
new file mode 100644
index 0000000..b2307e7
--- /dev/null
+++ b/packages/SystemUI/res/layout/bubble_expanded_view.xml
@@ -0,0 +1,30 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+  ~ Copyright (C) 2018 The Android Open Source Project
+  ~
+  ~ Licensed under the Apache License, Version 2.0 (the "License");
+  ~ you may not use this file except in compliance with the License.
+  ~ You may obtain a copy of the License at
+  ~
+  ~      http://www.apache.org/licenses/LICENSE-2.0
+  ~
+  ~ Unless required by applicable law or agreed to in writing, software
+  ~ distributed under the License is distributed on an "AS IS" BASIS,
+  ~ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  ~ See the License for the specific language governing permissions and
+  ~ limitations under the License
+  -->
+<com.android.systemui.bubbles.BubbleExpandedViewContainer
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_height="wrap_content"
+    android:layout_width="match_parent"
+    android:id="@+id/bubble_expanded_view">
+
+    <!-- TODO: header -->
+
+    <View
+        android:id="@+id/pointer_view"
+        android:layout_width="@dimen/bubble_pointer_width"
+        android:layout_height="@dimen/bubble_pointer_height"
+    />
+</com.android.systemui.bubbles.BubbleExpandedViewContainer>