Replace OVERRIDE->override and FINAL->final since we now require C++11.

src/heap/mark-compact.cc

Index: src/heap/mark-compact.cc
diff --git a/src/heap/mark-compact.cc b/src/heap/mark-compact.cc
index 94fc931b9b4cfe31f8c794337b6529ce0f4a02d4..f2a98527b139e7099db9f38c64e1844c96a41b59 100644
--- a/src/heap/mark-compact.cc
+++ b/src/heap/mark-compact.cc
@@ -482,7 +482,7 @@ class MarkCompactCollector::SweeperTask : public v8::Task {
 
  private:
   // v8::Task overrides.
-  void Run() OVERRIDE {
+  void Run() override {
     heap_->mark_compact_collector()->SweepInParallel(space_, 0);
     heap_->mark_compact_collector()->pending_sweeper_jobs_semaphore_.Signal();
   }