Track initializers already seen (fixes #21439)

pkg/polymer/lib/src/build/script_compactor.dart

Index: pkg/polymer/lib/src/build/script_compactor.dart
diff --git a/pkg/polymer/lib/src/build/script_compactor.dart b/pkg/polymer/lib/src/build/script_compactor.dart
index 20d805287fcc472d0d4c662559f97d5fdd5647fc..bd3b3d8da21d70716ff5503d1504900f90df40da 100644
--- a/pkg/polymer/lib/src/build/script_compactor.dart
+++ b/pkg/polymer/lib/src/build/script_compactor.dart
@@ -249,13 +249,15 @@ class _ScriptCompactor extends PolymerTransformer {
     // Process all classes and top-level functions to include initializers,
     // register custom elements, and include special fields and methods in
     // custom element classes.
+    var functionsSeen = new Set<FunctionElement>();
+    var classesSeen = new Set<ClassElement>();
     for (var id in entryLibraries) {
       var lib = resolver.getLibrary(id);
-      for (var fun in _visibleTopLevelMethodsOf(lib)) {
+      for (var fun in _visibleTopLevelMethodsOf(lib, functionsSeen)) {
         _processFunction(fun, id);
       }
 
-      for (var cls in _visibleClassesOf(lib)) {
+      for (var cls in _visibleClassesOf(lib, classesSeen)) {
         _processClass(cls, id, recorder);
       }
     }
@@ -807,28 +809,41 @@ class _ResolvedTypes {
 
 /// Retrieves all classses that are visible if you were to import [lib]. This
 /// includes exported classes from other libraries.
-List<ClassElement> _visibleClassesOf(LibraryElement lib) {
+List<ClassElement> _visibleClassesOf(LibraryElement lib,
+    Set<ClassElement> seen) {
   var result = [];
-  result.addAll(lib.units.expand((u) => u.types));
+  addAllNew(list) => list.forEach((e) {
+    if (!seen.contains(e)) result.add(e);
+  });
+  addAllNew(lib.units.expand((u) => u.types));
   for (var e in lib.exports) {
-    var exported = e.exportedLibrary.units.expand((u) => u.types).toList();
+    var exportedLibrary = e.exportedLibrary;
+    if (seen.contains(exportedLibrary)) continue;
+    var exported = exportedLibrary.units.expand((u) => u.types).toList();
     _filter(exported, e.combinators);
-    result.addAll(exported);
+    addAllNew(exported);
   }
+  seen.addAll(result);
   return result;
 }
 
 /// Retrieves all top-level methods that are visible if you were to import
 /// [lib]. This includes exported methods from other libraries too.
-List<FunctionElement> _visibleTopLevelMethodsOf(LibraryElement lib) {
+List<FunctionElement> _visibleTopLevelMethodsOf(
+    LibraryElement lib, Set<FunctionElement> seen) {
   var result = [];
-  result.addAll(lib.units.expand((u) => u.functions));
+  addAllNew(list) => list.forEach((e) {
+    if (!seen.contains(e)) result.add(e);
+  });
+  addAllNew(lib.units.expand((u) => u.functions));
   for (var e in lib.exports) {
-    var exported = e.exportedLibrary.units
-        .expand((u) => u.functions).toList();
+    var exportedLibrary = e.exportedLibrary;
+    if (seen.contains(exportedLibrary)) continue;
+    var exported = exportedLibrary.units.expand((u) => u.functions).toList();
     _filter(exported, e.combinators);
-    result.addAll(exported);
+    addAllNew(exported);
   }
+  seen.addAll(result);
   return result;
 }