Add the "virtual" keyword on method overrides that are missing it.

base/file_descriptor_shuffle.h

Index: base/file_descriptor_shuffle.h
diff --git a/base/file_descriptor_shuffle.h b/base/file_descriptor_shuffle.h
index a5c08e4359fd9bf4c832acadf5df58df4209ca8b..e1930352cfcddeed25e5631695fd020db30e8d5f 100644
--- a/base/file_descriptor_shuffle.h
+++ b/base/file_descriptor_shuffle.h
@@ -46,9 +46,9 @@ class InjectionDelegate {
 // An implementation of the InjectionDelegate interface using the file
 // descriptor table of the current process as the domain.
 class FileDescriptorTableInjection : public InjectionDelegate {
-  bool Duplicate(int* result, int fd);
-  bool Move(int src, int dest);
-  void Close(int fd);
+  virtual bool Duplicate(int* result, int fd);
+  virtual bool Move(int src, int dest);
+  virtual void Close(int fd);
 };
 
 // A single arc of the directed graph which describes an injective multimapping.