3/n Refactor TaskContainers to TaskDisplayArea

Renamed TaskContainers to TaskDisplayArea and added getDisplayArea()
method to WindowContainer that finds the first display area in the
hierarchy above the node. ActivityRecord and Task override it to
return the TaskDisplayArea class.

Bug: 152116619
Test: WM CTS and unit tests
Change-Id: I4525afbcd794848e1020213cdca04d89a646dd55
diff --git a/services/tests/wmtests/src/com/android/server/wm/DisplayContentTests.java b/services/tests/wmtests/src/com/android/server/wm/DisplayContentTests.java
index 5b96c43..fb1749d 100644
--- a/services/tests/wmtests/src/com/android/server/wm/DisplayContentTests.java
+++ b/services/tests/wmtests/src/com/android/server/wm/DisplayContentTests.java
@@ -1080,15 +1080,16 @@
     @Test
     public void testGetOrCreateRootHomeTask_defaultDisplay() {
         DisplayContent defaultDisplay = mWm.mRoot.getDisplayContent(DEFAULT_DISPLAY);
+        TaskDisplayArea defaultTaskDisplayArea = defaultDisplay.mTaskContainers;
 
         // Remove the current home stack if it exists so a new one can be created below.
-        ActivityStack homeTask = defaultDisplay.getRootHomeTask();
+        ActivityStack homeTask = defaultTaskDisplayArea.getRootHomeTask();
         if (homeTask != null) {
-            defaultDisplay.removeStack(homeTask);
+            defaultTaskDisplayArea.removeChild(homeTask);
         }
-        assertNull(defaultDisplay.getRootHomeTask());
+        assertNull(defaultTaskDisplayArea.getRootHomeTask());
 
-        assertNotNull(defaultDisplay.mTaskContainers.getOrCreateRootHomeTask());
+        assertNotNull(defaultTaskDisplayArea.getOrCreateRootHomeTask());
     }
 
     @Test
@@ -1098,31 +1099,34 @@
         doReturn(false).when(display).isUntrustedVirtualDisplay();
 
         // Remove the current home stack if it exists so a new one can be created below.
-        ActivityStack homeTask = display.getRootHomeTask();
+        TaskDisplayArea taskDisplayArea = display.mTaskContainers;
+        ActivityStack homeTask = taskDisplayArea.getRootHomeTask();
         if (homeTask != null) {
-            display.removeStack(homeTask);
+            taskDisplayArea.removeChild(homeTask);
         }
-        assertNull(display.getRootHomeTask());
+        assertNull(taskDisplayArea.getRootHomeTask());
 
-        assertNotNull(display.mTaskContainers.getOrCreateRootHomeTask());
+        assertNotNull(taskDisplayArea.getOrCreateRootHomeTask());
     }
 
     @Test
     public void testGetOrCreateRootHomeTask_unsupportedSystemDecorations() {
         DisplayContent display = createNewDisplay();
+        TaskDisplayArea taskDisplayArea = display.mTaskContainers;
         doReturn(false).when(display).supportsSystemDecorations();
 
-        assertNull(display.getRootHomeTask());
-        assertNull(display.mTaskContainers.getOrCreateRootHomeTask());
+        assertNull(taskDisplayArea.getRootHomeTask());
+        assertNull(taskDisplayArea.getOrCreateRootHomeTask());
     }
 
     @Test
     public void testGetOrCreateRootHomeTask_untrustedVirtualDisplay() {
         DisplayContent display = createNewDisplay();
+        TaskDisplayArea taskDisplayArea = display.mTaskContainers;
         doReturn(true).when(display).isUntrustedVirtualDisplay();
 
-        assertNull(display.getRootHomeTask());
-        assertNull(display.mTaskContainers.getOrCreateRootHomeTask());
+        assertNull(taskDisplayArea.getRootHomeTask());
+        assertNull(taskDisplayArea.getOrCreateRootHomeTask());
     }
 
     private boolean isOptionsPanelAtRight(int displayId) {