Update more directories under src/ to follow C++11 style rule for {virtual,override}.

src/opts/SkXfermode_opts_arm_neon.h

 #ifndef SkXfermode_opts_arm_neon_DEFINED
 #define SkXfermode_opts_arm_neon_DEFINED
 
 #include "SkXfermode_proccoeff.h"
 
 class SkNEONProcCoeffXfermode : public SkProcCoeffXfermode {
 public:
     SkNEONProcCoeffXfermode(const ProcCoeff& rec, SkXfermode::Mode mode,
                             void* procSIMD)
             : INHERITED(rec, mode), fProcSIMD(procSIMD) {}
 
-    virtual void xfer32(SkPMColor dst[], const SkPMColor src[], int count,
-                        const SkAlpha aa[]) const override;
-    virtual void xfer16(uint16_t* SK_RESTRICT dst, const SkPMColor* SK_RESTRICT src,
-                        int count, const SkAlpha* SK_RESTRICT aa) const override;
+    void xfer32(SkPMColor dst[], const SkPMColor src[], int count,
+                const SkAlpha aa[]) const override;
+    void xfer16(uint16_t* SK_RESTRICT dst, const SkPMColor* SK_RESTRICT src,
+                int count, const SkAlpha* SK_RESTRICT aa) const override;
 
     SK_TO_STRING_OVERRIDE()
 
 private:
     // void* is used to avoid pulling arm_neon.h in the core and having to build
     // it with -mfpu=neon.
     void* fProcSIMD;
     typedef SkProcCoeffXfermode INHERITED;
 };
 
 extern SkPMColor srcatop_modeproc_neon(SkPMColor src, SkPMColor dst);
 extern SkPMColor dstatop_modeproc_neon(SkPMColor src, SkPMColor dst);
 extern SkPMColor xor_modeproc_neon(SkPMColor src, SkPMColor dst);
 extern SkPMColor plus_modeproc_neon(SkPMColor src, SkPMColor dst);
 extern SkPMColor modulate_modeproc_neon(SkPMColor src, SkPMColor dst);
 
 #endif //#ifdef SkXfermode_opts_arm_neon_DEFINED