Remove superfluous 'virtual' specifiers in ART.

Remove 'virtual' specifier on methods already bearing the 'override'
specifier.

Test: mmma art
Change-Id: I114930969a5ca048d88de9ecd18e2c6403593e31
diff --git a/runtime/gc/task_processor_test.cc b/runtime/gc/task_processor_test.cc
index caa8802..7cb678b 100644
--- a/runtime/gc/task_processor_test.cc
+++ b/runtime/gc/task_processor_test.cc
@@ -33,7 +33,7 @@
      : HeapTask(NanoTime() + MsToNs(10)), task_processor_(task_processor), counter_(counter),
        max_recursion_(max_recursion) {
   }
-  virtual void Run(Thread* self) override {
+  void Run(Thread* self) override {
     if (max_recursion_ > 0) {
       task_processor_->AddTask(self,
                                new RecursiveTask(task_processor_, counter_, max_recursion_ - 1));
@@ -52,7 +52,7 @@
   WorkUntilDoneTask(TaskProcessor* task_processor, Atomic<bool>* done_running)
       : task_processor_(task_processor), done_running_(done_running) {
   }
-  virtual void Run(Thread* self) override {
+  void Run(Thread* self) override {
     task_processor_->RunAllTasks(self);
     done_running_->store(true, std::memory_order_seq_cst);
   }
@@ -105,7 +105,7 @@
   TestOrderTask(uint64_t expected_time, size_t expected_counter, size_t* counter)
      : HeapTask(expected_time), expected_counter_(expected_counter), counter_(counter) {
   }
-  virtual void Run(Thread* thread ATTRIBUTE_UNUSED) override {
+  void Run(Thread* thread ATTRIBUTE_UNUSED) override {
     ASSERT_EQ(*counter_, expected_counter_);
     ++*counter_;
   }