Refactor bitmap scaler to make it easier to migrate rest of chrome to use it

src/core/SkBitmapScaler.h

Index: src/core/SkBitmapScaler.h
diff --git a/src/core/SkBitmapScaler.h b/src/core/SkBitmapScaler.h
index d6636cf34ea9a44a794308c6f6a78303cdbf1e09..ef559df606c727c2342d6948098cc37d5295e5b8 100644
--- a/src/core/SkBitmapScaler.h
+++ b/src/core/SkBitmapScaler.h
@@ -83,8 +83,13 @@ public:
                        const SkBitmap& source,
                        ResizeMethod method,
                        float dest_width, float dest_height,
-                       const SkConvolutionProcs&,
                        SkBitmap::Allocator* allocator = NULL);
+
+     /** Platforms can also optionally overwrite the convolution functions
+        if we have SIMD versions of them.
+      */
+
+    static void PlatformConvolutionProcs(SkConvolutionProcs*);
 };
 
 #endif