Update scrubClass() to match CoreTestRunner.

AndroidTestCase.scrubClass() is quite aggressive, and would end up
clearing out final fields like these:

private static final byte[] TEST_DATA = new byte[1];

This change updates the logic to match InstrumentationCoreTestRunner
in the cleanup() method.

Change-Id: Iba455ea35b2628473ce0ccc1431ab47c1caad45c

core/java/android/test/AndroidTestCase.java

@@ -20,9 +20,11 @@ import android.content.ContentValues;
 import android.content.Context;
 import android.content.Intent;
 import android.net.Uri;
+
 import junit.framework.TestCase;
 
 import java.lang.reflect.Field;
+import java.lang.reflect.Modifier;
 
 /**
  * Extend this if you need to access Resources or other things that depend on Activity Context.
@@ -152,11 +154,11 @@ public class AndroidTestCase extends TestCase {
      * @throws IllegalAccessException
      */
     protected void scrubClass(final Class<?> testCaseClass)
-    throws IllegalAccessException {
+            throws IllegalAccessException {
         final Field[] fields = getClass().getDeclaredFields();
         for (Field field : fields) {
-            final Class<?> fieldClass = field.getDeclaringClass();
-            if (testCaseClass.isAssignableFrom(fieldClass) && !field.getType().isPrimitive()) {
+            if (!field.getType().isPrimitive() &&
+                    !Modifier.isStatic(field.getModifiers())) {
                 try {
                     field.setAccessible(true);
                     field.set(this, null);
@@ -170,6 +172,4 @@ public class AndroidTestCase extends TestCase {
             }
         }
     }
-
-
 }