Revert of de-proc sk_float_rsqrt

src/core/SkOpts.h

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkOpts_DEFINED
 #define SkOpts_DEFINED
 
 #include "SkMatrix.h"
 #include "SkTextureCompressor.h"
 #include "SkTypes.h"
 #include "SkXfermode.h"
 
 struct ProcCoeff;
 
 namespace SkOpts {
     // Call to replace pointers to portable functions with pointers to CPU-specific functions.
     // Thread-safe and idempotent.
     // Called by SkGraphics::Init(), and automatically #if SK_ALLOW_STATIC_GLOBAL_INITIALIZERS.
     void Init();
 
     // Declare function pointers here...
 
+    // Returns a fast approximation of 1.0f/sqrtf(x).
+    extern float (*rsqrt)(float);
+
     // See SkUtils.h
     extern void (*memset16)(uint16_t[], uint16_t, int);
     extern void (*memset32)(uint32_t[], uint32_t, int);
 
     // May return nullptr if we haven't specialized the given Mode.
     extern SkXfermode* (*create_xfermode)(const ProcCoeff&, SkXfermode::Mode);
 
     typedef void (*BoxBlur)(const SkPMColor*, int, const SkIRect& srcBounds, SkPMColor*, int, int, int, int, int);
     extern BoxBlur box_blur_xx, box_blur_xy, box_blur_yx;
 
@@ skipping 20 matching lines @@
     extern SkMatrix::MapPtsProc matrix_translate, matrix_scale_translate, matrix_affine;
 
     // Swizzle input into some sort of 8888 pixel, {premul,unpremul} x {rgba,bgra}.
     typedef void (*Swizzle_8888)(uint32_t*, const void*, int);
     extern Swizzle_8888 RGBA_to_BGRA,  // i.e. just swap RB
                         RGBA_to_rgbA,  // i.e. just premultiply
                         RGBA_to_bgrA;  // i.e. swap RB and premultiply
 }
 
 #endif//SkOpts_DEFINED