Fix google-explicit-constructor warnings.

Bug: 28341362
Change-Id: I625fbab25f16282c2ea929cd16283d9d146fa17b
diff --git a/media/libmedia/IEffectClient.cpp b/media/libmedia/IEffectClient.cpp
index 1322e72..3f2c67d 100644
--- a/media/libmedia/IEffectClient.cpp
+++ b/media/libmedia/IEffectClient.cpp
@@ -33,7 +33,7 @@
 class BpEffectClient: public BpInterface<IEffectClient>
 {
 public:
-    BpEffectClient(const sp<IBinder>& impl)
+    explicit BpEffectClient(const sp<IBinder>& impl)
         : BpInterface<IEffectClient>(impl)
     {
     }