Fix SkImageFilterCache race

BUG=chromium:668937
R=reed@google.com,robertphillips@google.com

Change-Id: I72ceaf1d88946c277a38f32014640e01ae9cbded
Reviewed-on: https://skia-review.googlesource.com/6954
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Florin Malita <fmalita@chromium.org>
diff --git a/tests/ImageFilterCacheTest.cpp b/tests/ImageFilterCacheTest.cpp
index e0aceda..650d4cb 100644
--- a/tests/ImageFilterCacheTest.cpp
+++ b/tests/ImageFilterCacheTest.cpp
@@ -41,7 +41,7 @@
 
     SkIPoint foundOffset;
 
-    SkSpecialImage* foundImage = cache->get(key1, &foundOffset);
+    sk_sp<SkSpecialImage> foundImage = cache->get(key1, &foundOffset);
     REPORTER_ASSERT(reporter, foundImage);
     REPORTER_ASSERT(reporter, offset == foundOffset);