Make CollectionTest and Collection8Test abstract.

These classes are meant to be extended, but the test runner
tries to run them anyway which causes a warning message to
surfaced as a test result. Making them abstract allows
them to be used by subclasses.

bug: 28503384
Change-Id: I45c34dde7f045aa6721352508df463c69c2cd8ef

jsr166-tests/src/test/java/jsr166/Collection8Test.java

@@ -26,7 +26,8 @@ import junit.framework.Test;
  * Contains tests applicable to all jdk8+ Collection implementations.
  * An extension of CollectionTest.
  */
-public class Collection8Test extends JSR166TestCase {
+// Android-changed: Made class abstract so it will be ignored by test runners.
+public abstract class Collection8Test extends JSR166TestCase {
     final CollectionImplementation impl;
 
     /** Tests are parameterized by a Collection implementation. */

jsr166-tests/src/test/java/jsr166/CollectionTest.java

@@ -14,7 +14,8 @@ import junit.framework.Test;
 /**
  * Contains tests applicable to all Collection implementations.
  */
-class CollectionTest extends JSR166TestCase {
+// Android-changed: Made class abstract so it will be ignored by test runners.
+abstract class CollectionTest extends JSR166TestCase {
     final CollectionImplementation impl;
 
     /** Tests are parameterized by a Collection implementation. */