Fix google-explicit-constructor warnings.

Bug: 28341362
Change-Id: I7e061f68acdde368a3b63c029b928133646ebff2
diff --git a/libs/binder/IMediaResourceMonitor.cpp b/libs/binder/IMediaResourceMonitor.cpp
index 4800f5b..77e3d23 100644
--- a/libs/binder/IMediaResourceMonitor.cpp
+++ b/libs/binder/IMediaResourceMonitor.cpp
@@ -25,7 +25,7 @@
 
 class BpMediaResourceMonitor : public BpInterface<IMediaResourceMonitor> {
 public:
-    BpMediaResourceMonitor(const sp<IBinder>& impl)
+    explicit BpMediaResourceMonitor(const sp<IBinder>& impl)
         : BpInterface<IMediaResourceMonitor>(impl) {}
 
     virtual void notifyResourceGranted(/*in*/ int32_t pid, /*in*/ const int32_t type)