Tron logging - Fix isValidValue to match its name, allow nulls.

Test: runtest --path frameworks/base/core/tests/coretests/src/android/metrics/LogMakerTest.java
Change-Id: I92567e1873c5178606ac88135b5934d760b4ec24

core/java/android/metrics/LogMaker.java

@@ -106,7 +106,7 @@ public class LogMaker {
      * @return
      */
     public LogMaker addTaggedData(int tag, Object value) {
-        if (isValidValue(value)) {
+        if (!isValidValue(value)) {
             throw new IllegalArgumentException(
                     "Value must be loggable type - int, long, float, String");
         }
@@ -119,10 +119,14 @@ public class LogMaker {
     }
 
     public boolean isValidValue(Object value) {
-        return !(value instanceof Integer ||
+        if (value == null) {
+            Log.i("LogBuilder", "Logging a null value.");
+            return true;
+        }
+        return value instanceof Integer ||
             value instanceof String ||
             value instanceof Long ||
-            value instanceof Float);
+            value instanceof Float;
     }
 
     public Object getTaggedData(int tag) {

core/tests/coretests/src/android/metrics/LogMakerTest.java

@@ -100,6 +100,7 @@ public class LogMakerTest extends TestCase {
         builder.addTaggedData(2, 123);
         builder.addTaggedData(3, 123L);
         builder.addTaggedData(4, 123.0F);
+        builder.addTaggedData(5, null);
         Object[] out = builder.serialize();
         assertEquals("onetwothree", out[1]);
         assertEquals(123, out[3]);