[SettingsProvider] perf test for null settings

This is to track performance differences before and after the
cache optimization for null settings.

BUG: 228619157
Test: atest android.provider.SettingsProviderPerfTest
Change-Id: I04590d4d692d12970aa6d53789770fbe426f2c0e

apct-tests/perftests/settingsprovider/src/android/provider/SettingsProviderPerfTest.java

@@ -39,6 +39,7 @@ public final class SettingsProviderPerfTest {
     private static final String NAMESPACE = "test@namespace";
     private static final String SETTING_NAME1 = "test:setting1";
     private static final String SETTING_NAME2 = "test-setting2";
+    private static final String UNSET_SETTING = "test_unset_setting";
 
     private final ContentResolver mContentResolver;
 
@@ -92,6 +93,14 @@ public final class SettingsProviderPerfTest {
         }
     }
 
+    @Test
+    public void testSettingsValueConsecutiveReadUnset() {
+        final BenchmarkState state = mPerfStatusReporter.getBenchmarkState();
+        while (state.keepRunning()) {
+            Settings.Secure.getString(mContentResolver, UNSET_SETTING);
+        }
+    }
+
     @Test
     public void testSettingsNamespaceConsecutiveRead() {
         final List<String> names = new ArrayList<>();