Add support for profile-based startup optimizations.

pkg/compiler/lib/src/js_emitter/startup_emitter/model_emitter.dart

Index: pkg/compiler/lib/src/js_emitter/startup_emitter/model_emitter.dart
diff --git a/pkg/compiler/lib/src/js_emitter/startup_emitter/model_emitter.dart b/pkg/compiler/lib/src/js_emitter/startup_emitter/model_emitter.dart
index 212011e291de7ca4573c1d9c1b216c73c3dcb252..af17969701beba577263ac5cdb85acac84301d3e 100644
--- a/pkg/compiler/lib/src/js_emitter/startup_emitter/model_emitter.dart
+++ b/pkg/compiler/lib/src/js_emitter/startup_emitter/model_emitter.dart
@@ -5,6 +5,7 @@
 library dart2js.js_emitter.startup_emitter.model_emitter;
 
 import 'dart:convert' show JsonEncoder;
+import 'dart:math' show Random;
 
 import 'package:js_runtime/shared/embedded_names.dart'
     show
@@ -191,7 +192,8 @@ class ModelEmitter {
     });
 
     writeMainFragment(mainFragment, mainCode,
-        isSplit: program.deferredFragments.isNotEmpty);
+        isSplit: program.deferredFragments.isNotEmpty ||
+            program.hasSoftDeferredClasses);
 
     if (backend.backendUsage.requiresPreamble && !backend.htmlLibraryIsLoaded) {
       reporter.reportHintMessage(NO_LOCATION_SPANNABLE, MessageKind.PREAMBLE);