Fix/suppress startop 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: I9e7b929cfa65c68f4cdb4710c1c5c6760d56e4d5
diff --git a/startop/view_compiler/main.cc b/startop/view_compiler/main.cc
index 9351dc3..55bfdc7 100644
--- a/startop/view_compiler/main.cc
+++ b/startop/view_compiler/main.cc
@@ -42,7 +42,7 @@
 
 class ViewCompilerXmlVisitor : public XMLVisitor {
  public:
-  ViewCompilerXmlVisitor(JavaLangViewBuilder* builder) : builder_(builder) {}
+  explicit ViewCompilerXmlVisitor(JavaLangViewBuilder* builder) : builder_(builder) {}
 
   bool VisitEnter(const XMLDocument& /*doc*/) override {
     builder_->Start();