Fix google-explicit-constructor warnings.

Bug: 28341362
Change-Id: I625fbab25f16282c2ea929cd16283d9d146fa17b
diff --git a/media/libmedia/IHDCP.cpp b/media/libmedia/IHDCP.cpp
index f3a8902..21e35f6 100644
--- a/media/libmedia/IHDCP.cpp
+++ b/media/libmedia/IHDCP.cpp
@@ -37,7 +37,7 @@
 };
 
 struct BpHDCPObserver : public BpInterface<IHDCPObserver> {
-    BpHDCPObserver(const sp<IBinder> &impl)
+    explicit BpHDCPObserver(const sp<IBinder> &impl)
         : BpInterface<IHDCPObserver>(impl) {
     }
 
@@ -58,7 +58,7 @@
 IMPLEMENT_META_INTERFACE(HDCPObserver, "android.hardware.IHDCPObserver");
 
 struct BpHDCP : public BpInterface<IHDCP> {
-    BpHDCP(const sp<IBinder> &impl)
+    explicit BpHDCP(const sp<IBinder> &impl)
         : BpInterface<IHDCP>(impl) {
     }