fix analysis issue caught by dart2js bots

tools/dom/templates/html/impl/impl_Node.darttemplate

Index: tools/dom/templates/html/impl/impl_Node.darttemplate
diff --git a/tools/dom/templates/html/impl/impl_Node.darttemplate b/tools/dom/templates/html/impl/impl_Node.darttemplate
index 640121d056b1fc690e504624830aa6314c189d14..b17787c93571376f735399b5147ca9b2b7492935 100644
--- a/tools/dom/templates/html/impl/impl_Node.darttemplate
+++ b/tools/dom/templates/html/impl/impl_Node.darttemplate
@@ -294,7 +294,8 @@ $(ANNOTATIONS)class $CLASSNAME$EXTENDS$IMPLEMENTS$NATIVESPEC {
 
   /** Gets the template instance that instantiated this node, if any. */
   @Experimental
-  TemplateInstance get templateInstance => mdvPackage(this).templateInstance;
+  TemplateInstance get templateInstance =>
+      TemplateElement.mdvPackage(this).templateInstance;
 
 $!MEMBERS
 }