don't rely on canvas being reference counted

BUG=skia:

Change-Id: Ibb9feeabd305fa53dcba69c7a383ed8efa7df3bc
Reviewed-on: https://skia-review.googlesource.com/5264
Reviewed-by: Mike Reed <reed@google.com>
Reviewed-by: Derek Sollenberger <djsollen@google.com>
Commit-Queue: Mike Reed <reed@google.com>
diff --git a/dm/DMSrcSinkAndroid.cpp b/dm/DMSrcSinkAndroid.cpp
index c78cc19..da2b924 100644
--- a/dm/DMSrcSinkAndroid.cpp
+++ b/dm/DMSrcSinkAndroid.cpp
@@ -48,7 +48,7 @@
         Error draw(SkCanvas* canvas) const override {
             // Pass through HWUI's upper layers to get operational transforms
             std::unique_ptr<android::Canvas> ac(android::Canvas::create_canvas(canvas));
-            sk_sp<android::uirenderer::SkiaCanvasProxy> scProxy
+            std::unique_ptr<android::uirenderer::SkiaCanvasProxy> scProxy
                 (new android::uirenderer::SkiaCanvasProxy(ac.get()));
 
             // Pass through another proxy to get paint transforms