Don't ref/unref the static src-over xp
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bug=chromium:570301

Review URL: https://codereview.chromium.org/1540363002
diff --git a/src/gpu/batches/GrDrawBatch.h b/src/gpu/batches/GrDrawBatch.h
index 9401c67..4d4209a 100644
--- a/src/gpu/batches/GrDrawBatch.h
+++ b/src/gpu/batches/GrDrawBatch.h
@@ -83,7 +83,7 @@
                            this->pipeline()->getCoverageFragmentProcessor(i).name(),
                            this->pipeline()->getCoverageFragmentProcessor(i).dumpInfo().c_str());
         }
-        string.appendf("XP: %s\n", this->pipeline()->getXferProcessor()->name());
+        string.appendf("XP: %s\n", this->pipeline()->getXferProcessor().name());
         return string;
     }