Add onDrawBitmapLattice(), avoid unnecessary bitmap->image copy

src/pdf/SkPDFCanvas.h

 /*
  * Copyright 2016 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 #ifndef SkPDFCanvas_DEFINED
 #define SkPDFCanvas_DEFINED
 
 #include "SkCanvas.h"
@@ skipping 22 matching lines @@
                          const SkPaint*,
                          SkCanvas::SrcRectConstraint) override;
 
     void onDrawBitmapRect(const SkBitmap&,
                           const SkRect*,
                           const SkRect&,
                           const SkPaint*,
                           SkCanvas::SrcRectConstraint) override;
 
     void onDrawImageLattice(const SkImage*,
-                            const Lattice& lattice,
-                            const SkRect& dst,
+                            const Lattice&,
+                            const SkRect&,
                             const SkPaint*) override;
 
+    void onDrawBitmapLattice(const SkBitmap&,
+                             const Lattice&,
+                             const SkRect&,
+                             const SkPaint*) override;
+
 private:
     typedef SkCanvas INHERITED;
 };
 
 #endif  // SkPDFCanvas_DEFINED