Fix/suppress libs/* google-explicit-constructor warnings

* Add explicit to conversion constructors/operators

Bug: 28341362
Test: make with WITH_TIDY=1 DEFAULT_GLOBAL_TIDY_CHECKS=-*,google-explicit-constructor
Change-Id: I31d45e4c6ff9fa69801a14c341f2da66baf565a0
diff --git a/libs/input/PointerController.cpp b/libs/input/PointerController.cpp
index 0a90f85..6c5f20c 100644
--- a/libs/input/PointerController.cpp
+++ b/libs/input/PointerController.cpp
@@ -39,7 +39,7 @@
     virtual ~WeakLooperCallback() { }
 
 public:
-    WeakLooperCallback(const wp<LooperCallback>& callback) :
+    explicit WeakLooperCallback(const wp<LooperCallback>& callback) :
         mCallback(callback) {
     }