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

src/pdf/SkPDFCanvas.h

Index: src/pdf/SkPDFCanvas.h
diff --git a/src/pdf/SkPDFCanvas.h b/src/pdf/SkPDFCanvas.h
index 76bb7e13e385e438a64d9d9c0da35eb5d9e50d2b..5040e9817d700459a64b14fc196a1c5285db14e5 100644
--- a/src/pdf/SkPDFCanvas.h
+++ b/src/pdf/SkPDFCanvas.h
@@ -40,10 +40,15 @@ protected:
                           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;
 };