fix up virtual / override stuff

BUG=skia:

Review URL: https://codereview.chromium.org/1210283002
diff --git a/src/core/SkCoreBlitters.h b/src/core/SkCoreBlitters.h
index 31f3397..b327039 100644
--- a/src/core/SkCoreBlitters.h
+++ b/src/core/SkCoreBlitters.h
@@ -73,12 +73,12 @@
 class SkA8_Blitter : public SkRasterBlitter {
 public:
     SkA8_Blitter(const SkPixmap& device, const SkPaint& paint);
-    virtual void blitH(int x, int y, int width);
-    virtual void blitAntiH(int x, int y, const SkAlpha antialias[], const int16_t runs[]);
-    virtual void blitV(int x, int y, int height, SkAlpha alpha);
-    virtual void blitRect(int x, int y, int width, int height);
-    virtual void blitMask(const SkMask&, const SkIRect&);
-    virtual const SkPixmap* justAnOpaqueColor(uint32_t*);
+    void blitH(int x, int y, int width) override;
+    void blitAntiH(int x, int y, const SkAlpha antialias[], const int16_t runs[]) override;
+    void blitV(int x, int y, int height, SkAlpha alpha) override;
+    void blitRect(int x, int y, int width, int height) override;
+    void blitMask(const SkMask&, const SkIRect&) override;
+    const SkPixmap* justAnOpaqueColor(uint32_t*) override;
 
 private:
     unsigned fSrcA;
@@ -94,9 +94,9 @@
     SkA8_Shader_Blitter(const SkPixmap& device, const SkPaint& paint,
                         SkShader::Context* shaderContext);
     virtual ~SkA8_Shader_Blitter();
-    virtual void blitH(int x, int y, int width);
-    virtual void blitAntiH(int x, int y, const SkAlpha antialias[], const int16_t runs[]);
-    virtual void blitMask(const SkMask&, const SkIRect&);
+    void blitH(int x, int y, int width) override;
+    void blitAntiH(int x, int y, const SkAlpha antialias[], const int16_t runs[]) override;
+    void blitMask(const SkMask&, const SkIRect&) override;
 
 private:
     SkXfermode* fXfermode;
@@ -114,12 +114,12 @@
 class SkARGB32_Blitter : public SkRasterBlitter {
 public:
     SkARGB32_Blitter(const SkPixmap& device, const SkPaint& paint);
-    virtual void blitH(int x, int y, int width);
-    virtual void blitAntiH(int x, int y, const SkAlpha antialias[], const int16_t runs[]);
-    virtual void blitV(int x, int y, int height, SkAlpha alpha);
-    virtual void blitRect(int x, int y, int width, int height);
-    virtual void blitMask(const SkMask&, const SkIRect&);
-    virtual const SkPixmap* justAnOpaqueColor(uint32_t*);
+    void blitH(int x, int y, int width) override;
+    void blitAntiH(int x, int y, const SkAlpha antialias[], const int16_t runs[]) override;
+    void blitV(int x, int y, int height, SkAlpha alpha) override;
+    void blitRect(int x, int y, int width, int height) override;
+    void blitMask(const SkMask&, const SkIRect&) override;
+    const SkPixmap* justAnOpaqueColor(uint32_t*) override;
     void blitAntiH2(int x, int y, U8CPU a0, U8CPU a1) override;
     void blitAntiV2(int x, int y, U8CPU a0, U8CPU a1) override;
 
@@ -140,7 +140,7 @@
 public:
     SkARGB32_Opaque_Blitter(const SkPixmap& device, const SkPaint& paint)
         : INHERITED(device, paint) { SkASSERT(paint.getAlpha() == 0xFF); }
-    virtual void blitMask(const SkMask&, const SkIRect&);
+    void blitMask(const SkMask&, const SkIRect&) override;
     void blitAntiH2(int x, int y, U8CPU a0, U8CPU a1) override;
     void blitAntiV2(int x, int y, U8CPU a0, U8CPU a1) override;
 
@@ -152,7 +152,7 @@
 public:
     SkARGB32_Black_Blitter(const SkPixmap& device, const SkPaint& paint)
         : INHERITED(device, paint) {}
-    virtual void blitAntiH(int x, int y, const SkAlpha antialias[], const int16_t runs[]);
+    void blitAntiH(int x, int y, const SkAlpha antialias[], const int16_t runs[]) override;
     void blitAntiH2(int x, int y, U8CPU a0, U8CPU a1) override;
     void blitAntiV2(int x, int y, U8CPU a0, U8CPU a1) override;