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

src/core/SkBitmapProcState.h

Index: src/core/SkBitmapProcState.h
diff --git a/src/core/SkBitmapProcState.h b/src/core/SkBitmapProcState.h
index 663bcb8be91b03722b314cd9c1e0bb5f3900404d..73d7e904b30b99d1f6f456e3aa4c90c934f1f95b 100644
--- a/src/core/SkBitmapProcState.h
+++ b/src/core/SkBitmapProcState.h
@@ -33,7 +33,6 @@
 #endif
 
 class SkPaint;
-struct SkConvolutionProcs;
 
 struct SkBitmapProcState {
 
@@ -104,12 +103,6 @@ struct SkBitmapProcState {
      */
     void platformProcs();
 
-    /** Platforms can also optionally overwrite the convolution functions
-        if we have SIMD versions of them.
-      */
-
-    void platformConvolutionProcs(SkConvolutionProcs*);
-
     /** Given the byte size of the index buffer to be passed to the matrix proc,
         return the maximum number of resulting pixels that can be computed
         (i.e. the number of SkPMColor values to be written by the sample proc).