Change ResultType#getXmlString to use name()

This makes it easier to parse later using valueOf(...).

Change-Id: Iad815c448c2eb1489d5f391623e576542413a06d
diff --git a/suite/pts/lib/commonutil/src/com/android/pts/util/ResultType.java b/suite/pts/lib/commonutil/src/com/android/pts/util/ResultType.java
index 499654d..cdf448b 100644
--- a/suite/pts/lib/commonutil/src/com/android/pts/util/ResultType.java
+++ b/suite/pts/lib/commonutil/src/com/android/pts/util/ResultType.java
@@ -21,23 +21,18 @@
  */
 public enum ResultType {
     /** lower score shows better performance */
-    LOWER_BETTER("lowerBetter"),
+    LOWER_BETTER,
     /** higher score shows better performance */
-    HIGHER_BETTER("higherBetter"),
+    HIGHER_BETTER,
     /** This value is not directly correlated with performance. */
-    NEUTRAL("neutral"),
+    NEUTRAL,
     /** presence of this type requires some attention although it may not be an error. */
-    WARNING("warning");
-
-    final private String mXmlString;
-    ResultType(String xmlString) {
-        mXmlString = xmlString;
-    }
+    WARNING;
 
     /**
      * Return string used in CTS XML report
      */
     public String getXmlString() {
-        return mXmlString;
+        return name().toLowerCase();
     }
 }