dart2js: register holder of constant in initial value of a static field.

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 7036bb73a526943aa7b76c7b6428ec600e21bedc..ce9adbaf99ae4a1a729658f71f5ceff49b552bbc 100644
--- a/pkg/compiler/lib/src/js_emitter/program_builder.dart
+++ b/pkg/compiler/lib/src/js_emitter/program_builder.dart
@@ -209,6 +209,9 @@ class ProgramBuilder {
   StaticField _buildStaticField(Element element) {
     JavaScriptConstantCompiler handler = backend.constants;
     ConstantValue initialValue = handler.getInitialValueFor(element).value;
+    // TODO(zarah): The holder should not be registered during building of
+    // a static field.
+    _registry.registerHolder(namer.globalObjectForConstant(initialValue));
     js.Expression code = _task.emitter.constantReference(initialValue);
     String name = namer.getNameOfGlobalField(element);
     bool isFinal = false;