Add RootTargetPreparer for explicitly specifying the root dependency am: 4cc5459

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/native/+/26804795

Change-Id: I93fc30977d946efe806b0e043a9e9e3b78b66847
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>

Author: desprezj

libs/gui/tests/AndroidTest.xml

@@ -18,6 +18,7 @@
         <option name="cleanup" value="true" />
         <option name="push" value="libgui_test->/data/local/tmp/libgui_test" />
     </target_preparer>
+    <target_preparer class="com.android.tradefed.targetprep.RootTargetPreparer" />
     <target_preparer class="com.android.tradefed.targetprep.DeviceSetup">
       <option name="force-skip-system-props" value="true" /> <!-- avoid restarting device -->
       <option name="screen-always-on" value="on" />