dart2js: don't emit unneeded native info.

pkg/compiler/lib/src/js_emitter/program_builder.dart

Index: pkg/compiler/lib/src/js_emitter/program_builder.dart
diff --git a/pkg/compiler/lib/src/js_emitter/program_builder.dart b/pkg/compiler/lib/src/js_emitter/program_builder.dart
index 2d22ead02315ee95bb458efb7d9fb5dbc76f3817..f7e3754eead1f72dc70bd6d64226856cbcb0e49a 100644
--- a/pkg/compiler/lib/src/js_emitter/program_builder.dart
+++ b/pkg/compiler/lib/src/js_emitter/program_builder.dart
@@ -117,9 +117,6 @@ class ProgramBuilder {
 
     _markEagerClasses();
 
-    bool containsNativeClasses =
-        nativeClasses.length != _unneededNativeClasses.length;
-
     List<Holder> holders = _registry.holders.toList(growable: false);
 
     return new Program(
@@ -128,7 +125,9 @@ class ProgramBuilder {
         _buildLoadMap(),
         _buildTypeToInterceptorMap(),
         _task.metadataCollector,
-        outputContainsNativeClasses: containsNativeClasses,
+        outputContainsNativeClasses:
+            _compiler.enqueuer.codegen.nativeEnqueuer
+                .hasInstantiatedNativeClasses(),

[floitsch, 2015/03/02 14:26:01]

Move it out into a variable (as was before).
Assert that nativeClasses wasn't empty.

rename Program field to "needsNativeSupport" ?

[zarah, 2015/03/02 15:40:35]

Done.

         outputContainsConstantList: _task.outputContainsConstantList,
         hasIsolateSupport: _compiler.hasIsolateSupport);
   }