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

include/core/SkMatrix.h

Index: include/core/SkMatrix.h
diff --git a/include/core/SkMatrix.h b/include/core/SkMatrix.h
index 0ebe3280e2180778fa6fa32564baf1fe401d5ee0..adebada445913521638fe13f3ec1a3c3303cbe38 100644
--- a/include/core/SkMatrix.h
+++ b/include/core/SkMatrix.h
@@ -591,11 +591,16 @@ public:
         return GetMapPtsProc(this->getType());
     }
 
+    /** Returns true if the matrix can be stepped in X (not complex
+        perspective).
+    */
+    bool isFixedStepInX() const;
+
     /** If the matrix can be stepped in X (not complex perspective)
-        then return true and if step[XY] is not null, return the step[XY] value.
-        If it cannot, return false and ignore step.
+        then return the step value.
+        If it cannot, behavior is undefined.
     */
-    bool fixedStepInX(SkScalar y, SkFixed* stepX, SkFixed* stepY) const;
+    SkVector fixedStepInX(SkScalar y) const;
 
     /** Efficient comparison of two matrices. It distinguishes between zero and
      *  negative zero. It will return false when the sign of zero values is the