Change SkMatrix::fixedStepInX to return SkVector rather than SkFixed.

src/core/SkShader.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.
  */
 
 #include "SkAtomics.h"
 #include "SkBitmapProcShader.h"
 #include "SkColorShader.h"
@@ skipping 172 matching lines @@
             srcA += 4;
         } while (--n != 0);
     } while (count > 0);
 #endif
 }
 
 SkShader::Context::MatrixClass SkShader::Context::ComputeMatrixClass(const SkMatrix& mat) {
     MatrixClass mc = kLinear_MatrixClass;
 
     if (mat.hasPerspective()) {
-        if (mat.fixedStepInX(0, nullptr, nullptr)) {
+        if (mat.isFixedStepInX()) {
             mc = kFixedStepInX_MatrixClass;
         } else {
             mc = kPerspective_MatrixClass;
         }
     }
     return mc;
 }
 
 //////////////////////////////////////////////////////////////////////////////
 
@@ skipping 150 matching lines @@
 #include "SkEmptyShader.h"
 
 void SkEmptyShader::toString(SkString* str) const {
     str->append("SkEmptyShader: (");
 
     this->INHERITED::toString(str);
 
     str->append(")");
 }
 #endif