Add drawBitmapLattice() API

src/core/SkLatticeIter.h

+/*
+ * Copyright 2015 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkLatticeIter_DEFINED
+#define SkLatticeIter_DEFINED
+
+#include "SkCanvas.h"
+#include "SkScalar.h"
+#include "SkTArray.h"
+
+struct SkIRect;
+struct SkRect;
+
+/**
+ *  Disect a lattice request into an sequence of src-rect / dst-rect pairs
+ */
+class SkLatticeIter {
+public:
+
+    static bool Valid(int imageWidth, int imageHeight, const SkCanvas::Lattice& lattice);
+
+    SkLatticeIter(int imageWidth, int imageHeight, const SkCanvas::Lattice& lattice,
+                  const SkRect& dst);
+
+    static bool Valid(int imageWidth, int imageHeight, const SkIRect& center);
+
+    SkLatticeIter(int imageWidth, int imageHeight, const SkIRect& center, const SkRect& dst);
+
+    /**
+     *  While it returns true, use src/dst to draw the image/bitmap
+     */
+    bool next(SkRect* src, SkRect* dst);
+
+private:
+    SkTArray<SkScalar> fSrcX;
+    SkTArray<SkScalar> fSrcY;
+    SkTArray<SkScalar> fDstX;
+    SkTArray<SkScalar> fDstY;
+
+    int fCurrX;
+    int fCurrY;
+    bool fDone;
+};
+
+#endif