Fix google-explicit-constructor warnings.

Bug: 28341362
Change-Id: I11fe54e9e968d8a53a66d5b1cefca9026d5a9d7a
diff --git a/media/libmedia/IMediaCodecService.cpp b/media/libmedia/IMediaCodecService.cpp
index dcf2b27..2d62419 100644
--- a/media/libmedia/IMediaCodecService.cpp
+++ b/media/libmedia/IMediaCodecService.cpp
@@ -33,7 +33,7 @@
 class BpMediaCodecService : public BpInterface<IMediaCodecService>
 {
 public:
-    BpMediaCodecService(const sp<IBinder>& impl)
+    explicit BpMediaCodecService(const sp<IBinder>& impl)
         : BpInterface<IMediaCodecService>(impl)
     {
     }