Fix build with new googletest

The new googletest requires prefix to be non-empty.

Change-Id: I3ebd13861c4803b53dbeb4ac5f247984814bef45
diff --git a/boot/1.1/vts/functional/VtsHalBootV1_1TargetTest.cpp b/boot/1.1/vts/functional/VtsHalBootV1_1TargetTest.cpp
index fba9a5e..7c58ef3 100644
--- a/boot/1.1/vts/functional/VtsHalBootV1_1TargetTest.cpp
+++ b/boot/1.1/vts/functional/VtsHalBootV1_1TargetTest.cpp
@@ -81,6 +81,6 @@
 }
 
 INSTANTIATE_TEST_SUITE_P(
-        , BootHidlTest,
+        PerInstance, BootHidlTest,
         testing::ValuesIn(android::hardware::getAllHalInstanceNames(IBootControl::descriptor)),
         android::hardware::PrintInstanceNameToString);
diff --git a/health/2.1/vts/functional/VtsHalHealthV2_1TargetTest.cpp b/health/2.1/vts/functional/VtsHalHealthV2_1TargetTest.cpp
index 7df4926..da9f5bb 100644
--- a/health/2.1/vts/functional/VtsHalHealthV2_1TargetTest.cpp
+++ b/health/2.1/vts/functional/VtsHalHealthV2_1TargetTest.cpp
@@ -252,7 +252,7 @@
 }
 
 INSTANTIATE_TEST_SUITE_P(
-        , HealthHidlTest,
+        PerInstance, HealthHidlTest,
         testing::ValuesIn(android::hardware::getAllHalInstanceNames(IHealth::descriptor)),
         android::hardware::PrintInstanceNameToString);
 
diff --git a/vibrator/aidl/vts/VtsHalVibratorTargetTest.cpp b/vibrator/aidl/vts/VtsHalVibratorTargetTest.cpp
index b0e6c72..d2977c6 100644
--- a/vibrator/aidl/vts/VtsHalVibratorTargetTest.cpp
+++ b/vibrator/aidl/vts/VtsHalVibratorTargetTest.cpp
@@ -228,7 +228,7 @@
     }
 }
 
-INSTANTIATE_TEST_SUITE_P(, VibratorAidl,
+INSTANTIATE_TEST_SUITE_P(Vibrator, VibratorAidl,
                          testing::ValuesIn(android::getAidlHalInstanceNames(IVibrator::descriptor)),
                          android::PrintInstanceNameToString);