Cleanup: Mark some overridden methods with 'SK_OVERRIDE'.

src/utils/SkTextureCompressor_Blitter.h

Index: src/utils/SkTextureCompressor_Blitter.h
diff --git a/src/utils/SkTextureCompressor_Blitter.h b/src/utils/SkTextureCompressor_Blitter.h
index 0c26a7a7eb853292c8daa284ec8369fd7a14e329..cdf2fb680d3633652befed7cb5f2afd13b113624 100644
--- a/src/utils/SkTextureCompressor_Blitter.h
+++ b/src/utils/SkTextureCompressor_Blitter.h
@@ -378,7 +378,7 @@ public:
      * to preserve semantics if blitAntiH doesn't get called in too many
      * weird ways...
      */
-    virtual int requestRowsPreserved() const { return BlockDim; }
+    virtual int requestRowsPreserved() const SK_OVERRIDE { return BlockDim; }
 
 private:
     static const int kPixelsPerBlock = BlockDim * BlockDim;