move SkScalarLog2 into its only client, in a move to reduce our public API surface area

include/core/SkScalar.h

 /*
  * Copyright 2006 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkScalar_DEFINED
 #define SkScalar_DEFINED
 
@@ skipping 198 matching lines @@
     If t is 0, return A
     If t is 1, return B
     else interpolate.
     t must be [0..SK_Scalar1]
 */
 static inline SkScalar SkScalarInterp(SkScalar A, SkScalar B, SkScalar t) {
     SkASSERT(t >= 0 && t <= SK_Scalar1);
     return A + SkScalarMul(B - A, t);
 }
 
-static inline SkScalar SkScalarLog2(SkScalar x) {
-    static const SkScalar log2_conversion_factor = SkScalarDiv(1, SkScalarLog(2));
-
-    return SkScalarMul(SkScalarLog(x), log2_conversion_factor);
-}
-
 /** Interpolate along the function described by (keys[length], values[length])
     for the passed searchKey.  SearchKeys outside the range keys[0]-keys[Length]
     clamp to the min or max value.  This function was inspired by a desire
     to change the multiplier for thickness in fakeBold; therefore it assumes
     the number of pairs (length) will be small, and a linear search is used.
     Repeated keys are allowed for discontinuous functions (so long as keys is
     monotonically increasing), and if key is the value of a repeated scalar in
     keys, the first one will be used.  However, that may change if a binary
     search is used.
 */
 SkScalar SkScalarInterpFunc(SkScalar searchKey, const SkScalar keys[],
                             const SkScalar values[], int length);
 
 /*
  *  Helper to compare an array of scalars.
  */
 static inline bool SkScalarsEqual(const SkScalar a[], const SkScalar b[], int n) {
     SkASSERT(n >= 0);
     for (int i = 0; i < n; ++i) {
         if (a[i] != b[i]) {
             return false;
         }
     }
     return true;
 }
 
 #endif