Reactivate tests #525

In this commit, the performance test from the Marker Test class is reactivated because it can be run quickly and successfully.
Contributes to #525

resources/tests/org.eclipse.core.tests.resources/src/org/eclipse/core/tests/resources/MarkerTest.java

@@ -235,7 +235,7 @@ public void _testPerformanceManyResources() {
 		}
 	}
 
-	public void _testPerformanceOneResource() {
+	public void testPerformanceOneResource() {
 		debug("testPerformanceOneResource");
 		long start;
 		long stop;