Use truncation, not rounding, when converting perlin noise seed (required by SVG spec).

src/effects/SkPerlinNoiseShader.cpp

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkDither.h"
 #include "SkPerlinNoiseShader.h"
 #include "SkColorFilter.h"
@@ skipping 106 matching lines @@
         if (result <= 0)
             result += kRandMaximum;
         fSeed = result;
         return result;
     }
 
     void init(SkScalar seed)
     {
         static const SkScalar gInvBlockSizef = SkScalarInvert(SkIntToScalar(kBlockSize));
 
+        // According to the SVG spec, we must truncate (not round) the seed value.
+        fSeed = SkScalarTruncToInt(seed);
         // The seed value clamp to the range [1, kRandMaximum - 1].
-        fSeed = SkScalarRoundToInt(seed);
         if (fSeed <= 0) {
             fSeed = -(fSeed % (kRandMaximum - 1)) + 1;
         }
         if (fSeed > kRandMaximum - 1) {
             fSeed = kRandMaximum - 1;
         }
         for (int channel = 0; channel < 4; ++channel) {
             for (int i = 0; i < kBlockSize; ++i) {
                 fLatticeSelector[i] = i;
                 fNoise[channel][i][0] = (random() % (2 * kBlockSize));
@@ skipping 1246 matching lines @@
     str->append(" seed: ");
     str->appendScalar(fSeed);
     str->append(" stitch tiles: ");
     str->append(fStitchTiles ? "true " : "false ");
 
     this->INHERITED::toString(str);
 
     str->append(")");
 }
 #endif