Replaced raw string arguments for Context.getSystemService() with final
Context variables

Change-Id: I97bb970fdb81f8c1329d112d60d644f6225f04f1
diff --git a/tests/tests/content/src/android/content/cts/ContextWrapperTest.java b/tests/tests/content/src/android/content/cts/ContextWrapperTest.java
index 1d9affa5..5e06d36 100644
--- a/tests/tests/content/src/android/content/cts/ContextWrapperTest.java
+++ b/tests/tests/content/src/android/content/cts/ContextWrapperTest.java
@@ -1203,7 +1203,7 @@
         assertNull(mContextWrapper.getSystemService("invalid"));
 
         // Test valid service name
-        assertNotNull(mContextWrapper.getSystemService("window"));
+        assertNotNull(mContextWrapper.getSystemService(Context.WINDOW_SERVICE));
     }
 
     @TestTargetNew(