Fix leak in ResourceCache test

Review URL: https://codereview.chromium.org/1359333004 .
diff --git a/tests/ResourceCacheTest.cpp b/tests/ResourceCacheTest.cpp
index a4dd2a5..0036f83 100644
--- a/tests/ResourceCacheTest.cpp
+++ b/tests/ResourceCacheTest.cpp
@@ -1253,7 +1253,7 @@
 static void test_abandoned(skiatest::Reporter* reporter) {
     Mock mock(10, 300);
     GrContext* context = mock.context();
-    TestResource* resource = new TestResource(context->getGpu());
+    SkAutoTUnref<GrGpuResource> resource(new TestResource(context->getGpu()));
     context->abandonContext();
 
     REPORTER_ASSERT(reporter, resource->wasDestroyed());