Make constructors explicit.

R=jkummerow@chromium.org
BUG=
TEST=

Review URL: https://chromiumcodereview.appspot.com/9368026

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@10666 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/ast.h

@@ -542,7 +542,7 @@ class ModuleLiteral: public Module {
  protected:
   template<class> friend class AstNodeFactory;
 
-  ModuleLiteral(Block* body)
+  explicit ModuleLiteral(Block* body)
       : body_(body) {
   }
 
@@ -560,7 +560,7 @@ class ModuleVariable: public Module {
  protected:
   template<class> friend class AstNodeFactory;
 
-  ModuleVariable(Variable* var)
+  explicit ModuleVariable(Variable* var)
       : var_(var) {
   }
 
@@ -599,7 +599,7 @@ class ModuleUrl: public Module {
  protected:
   template<class> friend class AstNodeFactory;
 
-  ModuleUrl(Handle<String> url) : url_(url) {
+  explicit ModuleUrl(Handle<String> url) : url_(url) {
   }
 
  private: