Fix google-explicit-constructor warnings in surfaceflinger.

* Add explicit keyword to conversion constructors,
  or use NOLINT for implicit converters.
Bug: 28341362
Test: build with WITH_TIDY=1

Change-Id: I94f511c3be31dc22022db6466ee9ed0c6be2bc8e
diff --git a/services/surfaceflinger/Client.h b/services/surfaceflinger/Client.h
index b6d7381..c77651f 100644
--- a/services/surfaceflinger/Client.h
+++ b/services/surfaceflinger/Client.h
@@ -38,7 +38,7 @@
 class Client : public BnSurfaceComposerClient
 {
 public:
-        Client(const sp<SurfaceFlinger>& flinger);
+        explicit Client(const sp<SurfaceFlinger>& flinger);
         ~Client();
 
     status_t initCheck() const;