Fix google-explicit-constructor warnings in art.

* Add explicit keyword to conversion constructors,
  or NOLINT for implicit converters.
Bug: 28341362
Test: build with WITH_TIDY=1

Change-Id: I1e1ee2661812944904fedadeff97b620506db47d
diff --git a/runtime/base/transform_array_ref.h b/runtime/base/transform_array_ref.h
index a4e0bc2..b432f86 100644
--- a/runtime/base/transform_array_ref.h
+++ b/runtime/base/transform_array_ref.h
@@ -72,7 +72,7 @@
 
   template <typename OtherBT,
             typename = typename std::enable_if<std::is_same<BaseType, const OtherBT>::value>::type>
-  TransformArrayRef(const TransformArrayRef<OtherBT, Function>& other)
+  TransformArrayRef(const TransformArrayRef<OtherBT, Function>& other)  // NOLINT, implicit
       : TransformArrayRef(other.base(), other.GetFunction()) { }
 
   // Assignment operators.