Fix google-explicit-constructor warnings.

Bug: 28341362
Change-Id: I625fbab25f16282c2ea929cd16283d9d146fa17b
diff --git a/media/libmedia/IDataSource.cpp b/media/libmedia/IDataSource.cpp
index 76d1d68..0be53c9 100644
--- a/media/libmedia/IDataSource.cpp
+++ b/media/libmedia/IDataSource.cpp
@@ -35,7 +35,8 @@
 };
 
 struct BpDataSource : public BpInterface<IDataSource> {
-    BpDataSource(const sp<IBinder>& impl) : BpInterface<IDataSource>(impl) {}
+    explicit BpDataSource(const sp<IBinder>& impl)
+        : BpInterface<IDataSource>(impl) {}
 
     virtual sp<IMemory> getIMemory() {
         Parcel data, reply;