Fix google-explicit-constructor warnings.

Bug: 28341362
Change-Id: I0ce850de85e0de6a5472dd142f738856142db9ec
diff --git a/libs/gui/IDisplayEventConnection.cpp b/libs/gui/IDisplayEventConnection.cpp
index 9890f44..b1d3b00 100644
--- a/libs/gui/IDisplayEventConnection.cpp
+++ b/libs/gui/IDisplayEventConnection.cpp
@@ -39,7 +39,7 @@
 class BpDisplayEventConnection : public BpInterface<IDisplayEventConnection>
 {
 public:
-    BpDisplayEventConnection(const sp<IBinder>& impl)
+    explicit BpDisplayEventConnection(const sp<IBinder>& impl)
         : BpInterface<IDisplayEventConnection>(impl)
     {
     }