Fix google-explicit-constructor warnings.

Bug: 28341362
Change-Id: I7e061f68acdde368a3b63c029b928133646ebff2
diff --git a/services/surfaceflinger/DispSync.cpp b/services/surfaceflinger/DispSync.cpp
index 37b6420..d438f2c 100644
--- a/services/surfaceflinger/DispSync.cpp
+++ b/services/surfaceflinger/DispSync.cpp
@@ -64,7 +64,7 @@
 class DispSyncThread: public Thread {
 public:
 
-    DispSyncThread(const char* name):
+    explicit DispSyncThread(const char* name):
             mName(name),
             mStop(false),
             mPeriod(0),