Fix google-explicit-constructor warnings.

Bug: 28341362
Change-Id: I0ce850de85e0de6a5472dd142f738856142db9ec
diff --git a/libs/gui/IGraphicBufferConsumer.cpp b/libs/gui/IGraphicBufferConsumer.cpp
index c4660ba..334611d 100644
--- a/libs/gui/IGraphicBufferConsumer.cpp
+++ b/libs/gui/IGraphicBufferConsumer.cpp
@@ -59,7 +59,7 @@
 class BpGraphicBufferConsumer : public BpInterface<IGraphicBufferConsumer>
 {
 public:
-    BpGraphicBufferConsumer(const sp<IBinder>& impl)
+    explicit BpGraphicBufferConsumer(const sp<IBinder>& impl)
         : BpInterface<IGraphicBufferConsumer>(impl)
     {
     }