Switch tests to test utility for counting nodes

Summary:
@public
replaces the global node counter with the event-based one for all tests.

Reviewed By: SidharthGuglani

Differential Revision: D15174856

fbshipit-source-id: f4401d502bdbaf3b6e4632a4d985aac260cb35a8

java/tests/com/facebook/yoga/YogaNodeTest.java

@@ -31,9 +31,9 @@ public class YogaNodeTest {
 
   @Test
   public void testInit() {
-    final int refCount = YogaNative.jni_YGNodeGetInstanceCount();
+    TestUtil.startCountingNodes();
     final YogaNode node = createNode();
-    assertEquals(refCount + 1, YogaNative.jni_YGNodeGetInstanceCount());
+    assertEquals(1, TestUtil.stopCountingNodes());
   }
 
   @Test