Fix google-explicit-constructor warnings.

Bug: 28341362
Change-Id: Ibdd6a210bb7ff228e3624cc319169f77aca3b51e
diff --git a/libs/hwui/renderstate/RenderState.cpp b/libs/hwui/renderstate/RenderState.cpp
index 84b6965..229aa46 100644
--- a/libs/hwui/renderstate/RenderState.cpp
+++ b/libs/hwui/renderstate/RenderState.cpp
@@ -186,7 +186,7 @@
 
 class DecStrongTask : public renderthread::RenderTask {
 public:
-    DecStrongTask(VirtualLightRefBase* object) : mObject(object) {}
+    explicit DecStrongTask(VirtualLightRefBase* object) : mObject(object) {}
 
     virtual void run() override {
         mObject->decStrong(nullptr);