Fix clang-tidy warnings in audio and playerservice.

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

Change-Id: I265f3b094e08d5705b506b3fbba51439c134af84
Merged-In: I265f3b094e08d5705b506b3fbba51439c134af84
diff --git a/media/libmediaplayerservice/SharedLibrary.h b/media/libmediaplayerservice/SharedLibrary.h
index 88451a0..fd02203 100644
--- a/media/libmediaplayerservice/SharedLibrary.h
+++ b/media/libmediaplayerservice/SharedLibrary.h
@@ -24,7 +24,7 @@
 namespace android {
     class SharedLibrary : public RefBase {
     public:
-        SharedLibrary(const String8 &path);
+        explicit SharedLibrary(const String8 &path);
         ~SharedLibrary();
 
         bool operator!() const;