Fix build break in dartdoc.

utils/dartdoc/dartdoc.dart

Index: utils/dartdoc/dartdoc.dart
diff --git a/utils/dartdoc/dartdoc.dart b/utils/dartdoc/dartdoc.dart
index 56c941465158fd305a5b956d6a8c596e6bde664c..96a60e8cb2370a7736855c83670a7d0c3a6744d4 100644
--- a/utils/dartdoc/dartdoc.dart
+++ b/utils/dartdoc/dartdoc.dart
@@ -905,6 +905,7 @@ class Dartdoc {
 
   /** Gets the URL for the documentation for [type]. */
   String typeUrl(Type type) {
+    if (type.isTop) return '${sanitize(type.library.name)}.html';
     // Always get the generic type to strip off any type parameters or
     // arguments. If the type isn't generic, genericType returns `this`, so it
     // works for non-generic types too.
@@ -913,7 +914,10 @@ class Dartdoc {
 
   /** Gets the URL for the documentation for [member]. */
   String memberUrl(Member member) {
-    return '${typeUrl(member.declaringType)}#${member.name}';
+    final typeUrl = typeUrl(member.declaringType);
+    if (!member.isConstructor) return '$typeUrl#${member.name}';
+    if (member.constructorName == '') return '$typeUrl#new:${member.name}';
+    return '$typeUrl#new:${member.name}.${member.constructorName}';
   }
 
   /** Gets the anchor id for the document for [member]. */