Standardize usage of virtual/override/final specifiers in base/.

base/memory/discardable_memory_shmem_allocator.cc

Index: base/memory/discardable_memory_shmem_allocator.cc
diff --git a/base/memory/discardable_memory_shmem_allocator.cc b/base/memory/discardable_memory_shmem_allocator.cc
index 78d15c1031e7713bc9e80915dd894942c4d755b6..8b9157f583adde720a7412510979a7a99ac7a5df 100644
--- a/base/memory/discardable_memory_shmem_allocator.cc
+++ b/base/memory/discardable_memory_shmem_allocator.cc
@@ -17,8 +17,8 @@ class DiscardableMemoryShmemAllocatorImpl
     : public DiscardableMemoryShmemAllocator {
  public:
   // Overridden from DiscardableMemoryShmemAllocator:
-  virtual scoped_ptr<DiscardableSharedMemory>
-  AllocateLockedDiscardableSharedMemory(size_t size) override {
+  scoped_ptr<DiscardableSharedMemory> AllocateLockedDiscardableSharedMemory(
+      size_t size) override {
     scoped_ptr<DiscardableSharedMemory> memory(new DiscardableSharedMemory);
     if (!memory->CreateAndMap(size))
       return scoped_ptr<DiscardableSharedMemory>();