Fix cpplint whitespace/parens issues

Change-Id: Ifc678d59a8bed24ffddde5a0e543620b17b0aba9
diff --git a/runtime/gc/heap.h b/runtime/gc/heap.h
index 630d063..32e068c 100644
--- a/runtime/gc/heap.h
+++ b/runtime/gc/heap.h
@@ -70,7 +70,7 @@
 
 class AgeCardVisitor {
  public:
-  byte operator ()(byte card) const {
+  byte operator()(byte card) const {
     if (card == accounting::CardTable::kCardDirty) {
       return card - 1;
     } else {