Fix build breakage.

Change-Id: Ie60b148d61d746de354b12852d4a6db2d82121c5
diff --git a/services/core/java/com/android/server/am/TaskRecord.java b/services/core/java/com/android/server/am/TaskRecord.java
index 51a9030..3fc6846 100644
--- a/services/core/java/com/android/server/am/TaskRecord.java
+++ b/services/core/java/com/android/server/am/TaskRecord.java
@@ -45,6 +45,7 @@
 import android.app.ActivityManager;
 import android.app.ActivityManager.StackId;
 import android.app.ActivityManager.TaskDescription;
+import android.app.ActivityManager.TaskThumbnail;
 import android.app.ActivityManager.TaskThumbnailInfo;
 import android.app.ActivityOptions;
 import android.app.AppGlobals;