Ignore unused classes when constructing set for deferred loading.

sdk/lib/_internal/compiler/implementation/deferred_load.dart

Index: sdk/lib/_internal/compiler/implementation/deferred_load.dart
diff --git a/sdk/lib/_internal/compiler/implementation/deferred_load.dart b/sdk/lib/_internal/compiler/implementation/deferred_load.dart
index 53eca9743ed7c90cbebcf36cd64e57b6d68b5c56..c6054a8823c0d138fc49ce28bfce45b4e6bf6d9b 100644
--- a/sdk/lib/_internal/compiler/implementation/deferred_load.dart
+++ b/sdk/lib/_internal/compiler/implementation/deferred_load.dart
@@ -153,22 +153,25 @@ class DeferredLoadTask extends CompilerTask {
       // If we see a class, add everything its instance members refer
       // to.  Static members are not relevant.
       ClassElement cls = element.declaration;
-      cls.forEachLocalMember((Element e) {
-        if (!e.isInstanceMember()) return;
-        result.addAll(DependencyCollector.collect(e.implementation, compiler));
-      });
-      if (cls.implementation != cls) {
-        // TODO(ahe): Why doesn't ClassElement.forEachLocalMember do this?
-        cls.implementation.forEachLocalMember((Element e) {
+      // Make sure that class has been used - type has been computed.
+      if (cls.thisType != null) {

[ahe, 2013/08/06 16:00:34]

I think this check belongs on line 92, and it feels like it should be a little
more general. Something like a method in Enqueuer:

bool isLive(Element element) {
  if (seenClasses.contains(element)) return true;
  if (getCachedElements(element) != null) return true;
  return false;
}

[aam-me, 2013/08/07 03:20:42]

Thanks, makes sense.
Done.

+        cls.forEachLocalMember((Element e) {
           if (!e.isInstanceMember()) return;
-          result.addAll(DependencyCollector.collect(e.implementation,
-                                                    compiler));
+          result.addAll(DependencyCollector.collect(e.implementation, compiler));
         });
+        if (cls.implementation != cls) {
+          // TODO(ahe): Why doesn't ClassElement.forEachLocalMember do this?
+          cls.implementation.forEachLocalMember((Element e) {
+            if (!e.isInstanceMember()) return;
+            result.addAll(DependencyCollector.collect(e.implementation,
+                                                      compiler));
+          });
+        }
+        for (var type in cls.allSupertypes) {
+          result.add(type.element.implementation);
+        }
+        result.add(cls.implementation);
       }
-      for (var type in cls.allSupertypes) {
-        result.add(type.element.implementation);
-      }
-      result.add(cls.implementation);
     } else if (Elements.isStaticOrTopLevel(element)
                || element.isConstructor()) {
       result.addAll(DependencyCollector.collect(element, compiler));