Fix google-explicit-constructor warnings.

Bug: 28341362
Change-Id: I0ce850de85e0de6a5472dd142f738856142db9ec
diff --git a/libs/gui/ISurfaceComposerClient.cpp b/libs/gui/ISurfaceComposerClient.cpp
index 2ecb908..decffbf 100644
--- a/libs/gui/ISurfaceComposerClient.cpp
+++ b/libs/gui/ISurfaceComposerClient.cpp
@@ -47,7 +47,7 @@
 class BpSurfaceComposerClient : public BpInterface<ISurfaceComposerClient>
 {
 public:
-    BpSurfaceComposerClient(const sp<IBinder>& impl)
+    explicit BpSurfaceComposerClient(const sp<IBinder>& impl)
         : BpInterface<ISurfaceComposerClient>(impl) {
     }