add drawImageNine
this also exposes nine-patch drawing directly to devices, and creates a shared iterator for unrolling a nine-patch into single rect->rect draws.

BUG=skia:

Review URL: https://codereview.chromium.org/1211583003
diff --git a/src/core/SkPictureRecord.h b/src/core/SkPictureRecord.h
index cee5ea3..e2d5f7d 100644
--- a/src/core/SkPictureRecord.h
+++ b/src/core/SkPictureRecord.h
@@ -188,6 +188,8 @@
     void onDrawImage(const SkImage*, SkScalar left, SkScalar top, const SkPaint*) override;
     void onDrawImageRect(const SkImage*, const SkRect* src, const SkRect& dst,
                          const SkPaint*) override;
+    void onDrawImageNine(const SkImage*, const SkIRect& center, const SkRect& dst,
+                         const SkPaint*) override;
     void onDrawBitmapNine(const SkBitmap&, const SkIRect& center, const SkRect& dst,
                           const SkPaint*) override;
     void onDrawSprite(const SkBitmap&, int left, int top, const SkPaint*) override;