dart2js: Add a header to the output of the startup emitter.

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 e30c58b0623fbef2a47fc59f03f837e8ad49100b..ed243002f0ceee9bc149e56912bc8a6dd1f69b53 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
@@ -34,6 +34,7 @@ import '../../util/util.dart' show
 import '../../util/uri_extras.dart' show
     relativize;
 
+import '../headers.dart';
 import '../js_emitter.dart' show AstContainer, NativeEmitter;
 
 import 'package:js_runtime/shared/embedded_names.dart' show
@@ -218,11 +219,11 @@ class ModelEmitter {
   }
 
   /// Generates a simple header that provides the compiler's build id.
-  String buildGeneratedBy(compiler) {
-    var suffix = '';
-    if (compiler.hasBuildId) suffix = ' version: ${compiler.buildId}';
-    return '// Generated by dart2js (fast startup), '
-        'the Dart to JavaScript compiler$suffix.\n';
+  js.Comment buildGeneratedBy() {
+    String flavor = compiler.useContentSecurityPolicy
+        ? 'fast startup, CSP'
+        : 'fast startup';
+    return new js.Comment(generatedBy(compiler, flavor: flavor));
   }
 
   /// Writes all deferred fragment's code into files.
@@ -258,7 +259,12 @@ class ModelEmitter {
             codeOutputListeners);
     outputBuffers[fragment] = mainOutput;
 
-    mainOutput.addBuffer(js.prettyPrint(code, compiler,
+    js.Program program = new js.Program([
+        buildGeneratedBy(),
+        new js.Comment(HOOKS_API_USAGE),
+        code]);
+
+    mainOutput.addBuffer(js.prettyPrint(program, compiler,
         monitor: compiler.dumpInfoTask));
 
     if (shouldGenerateSourceMap) {
@@ -307,9 +313,11 @@ class ModelEmitter {
     //   deferredInitializer.current = <pretty-printed code>;
     //   deferredInitializer[<hash>] = deferredInitializer.current;
 
-    output.add('\n${deferredInitializersGlobal}.current = ');
+    js.Program program = new js.Program([
+        buildGeneratedBy(),
+        js.js.statement('$deferredInitializersGlobal.current = #', code)]);
 
-    output.addBuffer(js.prettyPrint(code, compiler,
+    output.addBuffer(js.prettyPrint(program, compiler,
         monitor: compiler.dumpInfoTask));
 
     // Make a unique hash of the code (before the sourcemaps are added)