Fix clang-tidy warnings in drm.

* Add explicit keyword to conversion constructors.
Bug: 28341362
* Use const reference type for read-only parameters.
Bug: 30407689
* Use const reference type to avoid unnecessary copy.
Bug: 30413862
Test: build with WITH_TIDY=1

Change-Id: Idf1c48d7bfe3f0da20401cb3ff1983ec00be170d
diff --git a/include/drm/DrmInfoEvent.h b/include/drm/DrmInfoEvent.h
index dfca228..3165f02 100644
--- a/include/drm/DrmInfoEvent.h
+++ b/include/drm/DrmInfoEvent.h
@@ -77,7 +77,7 @@
      * @param[in] infoType Type of information
      * @param[in] message Message description
      */
-    DrmInfoEvent(int uniqueId, int infoType, const String8 message);
+    DrmInfoEvent(int uniqueId, int infoType, const String8& message);
 
     /**
      * Destructor for DrmInfoEvent