Restore counting iterations in computeContainsDeclaration cycle detector

A follow-up change to bug 509898 missed actually incrementing the counter,
restore it now.

Fixes: 5462bac ("Bug 509898 - IndexFileSet.containsDeclaration is slow and is causing UI freezes")

core/org.eclipse.cdt.core/parser/org/eclipse/cdt/internal/core/index/IndexFileSet.java

@@ -100,6 +100,11 @@ private boolean computeContainsDeclaration(IIndexBinding binding) {
 					Set<Long> visited = null;
 					long nameRecord;
 					while ((nameRecord = nameIterator.next()) != 0) {
+						if (++iterationCount >= 1000 && visited == null) {
+							// Iteration count is suspiciously high. Start keeping track of visited names
+							// to be able to detect a cycle.
+							visited = new HashSet<>();
+						}
 						if (visited != null && !visited.add(nameRecord)) {
 							// Cycle detected!
 							logInvalidNameChain(pdom, binding);
@@ -114,12 +119,6 @@ private boolean computeContainsDeclaration(IIndexBinding binding) {
 							}
 							return true;
 						}
-						if (iterationCount >= 1000 && visited == null) {
-							// Iteration count is suspiciously high. Start keeping track of visited names
-							// to be able to detect a cycle.
-							visited = new HashSet<>();
-							visited.add(nameRecord);
-						}
 					}
 				}
 			} catch (CoreException e) {