Mark methods with override in pdf/

pdf/pdf.h

Index: pdf/pdf.h
diff --git a/pdf/pdf.h b/pdf/pdf.h
index 37e72e510be95cffb2768fb3c8e3d049bdadda55..342757f24626cc33ba99468ea59001436c55efc2 100644
--- a/pdf/pdf.h
+++ b/pdf/pdf.h
@@ -13,11 +13,11 @@ namespace chrome_pdf {
 class PDFModule : public pp::Module {
  public:
   PDFModule();
-  virtual ~PDFModule();
+  ~PDFModule() override;
 
   // pp::Module implementation.
-  virtual bool Init();
-  virtual pp::Instance* CreateInstance(PP_Instance instance);
+  bool Init() override;
+  pp::Instance* CreateInstance(PP_Instance instance) override;
 };
 
 int PPP_InitializeModule(PP_Module module_id,