Change ScalarTo256 to more efficient implementation.

src/core/SkDraw.cpp

 /*
  * 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.
  */
 #define __STDC_LIMIT_MACROS
 
 #include "SkDraw.h"
 #include "SkBlitter.h"
@@ skipping 1743 matching lines @@
         return false;
     }
     fDstToUnit.setConcat(im, ctmInv);
     return true;
 }
 
 #include "SkColorPriv.h"
 #include "SkComposeShader.h"
 
 static int ScalarTo256(SkScalar v) {
-    int scale = SkScalarToFixed(v) >> 8;
-    if (scale < 0) {
-        scale = 0;
-    }
-    if (scale > 255) {
-        scale = 255;
-    }
-    return SkAlpha255To256(scale);
+    return static_cast<int>(SkScalarPin(v, 0, 1) * 256);
 }
 
 
 SkTriColorShader::TriColorShaderContext::TriColorShaderContext(const SkTriColorShader& shader,
                                                                const ContextRec& rec)
     : INHERITED(shader, rec) {}
 
 SkTriColorShader::TriColorShaderContext::~TriColorShaderContext() {}
 
 size_t SkTriColorShader::contextSize() const {
@@ skipping 280 matching lines @@
         mask->fImage = SkMask::AllocImage(size);
         memset(mask->fImage, 0, mask->computeImageSize());
     }
 
     if (SkMask::kJustComputeBounds_CreateMode != mode) {
         draw_into_mask(*mask, devPath, style);
     }
 
     return true;
 }