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

pkg/compiler/lib/src/js_emitter/full_emitter/declarations.dart

Index: pkg/compiler/lib/src/js_emitter/full_emitter/declarations.dart
diff --git a/pkg/compiler/lib/src/js_emitter/full_emitter/declarations.dart b/pkg/compiler/lib/src/js_emitter/full_emitter/declarations.dart
index 01fda29d470a88f9b14fa20ecf4cafc81fa714f8..0bc38d330e758638dbe1bc1af12c6af5fbd53152 100644
--- a/pkg/compiler/lib/src/js_emitter/full_emitter/declarations.dart
+++ b/pkg/compiler/lib/src/js_emitter/full_emitter/declarations.dart
@@ -13,28 +13,6 @@ const DEBUG_FAST_OBJECTS = false;
 typedef jsAst.Property AddPropertyFunction(jsAst.Name name,
                                            jsAst.Expression value);
 
-const String GENERATED_BY = """
-// Generated by dart2js, the Dart to JavaScript compiler.
-""";
-
-const String HOOKS_API_USAGE = """
-// The code supports the following hooks:
-// dartPrint(message):
-//    if this function is defined it is called instead of the Dart [print]
-//    method.
-//
-// dartMainRunner(main, args):
-//    if this function is defined, the Dart [main] method will not be invoked
-//    directly. Instead, a closure that will invoke [main], and its arguments
-//    [args] is passed to [dartMainRunner].
-//
-// dartDeferredLibraryLoader(uri, successCallback, errorCallback):
-//    if this function is defined, it will be called when a deferered library
-//    is loaded. It should load and eval the javascript of `uri`, and call
-//    successCallback. If it fails to do so, it should call errorCallback with
-//    an error.
-""";
-
 // Compact field specifications.  The format of the field specification is
 // <accessorName>:<fieldName><suffix> where the suffix and accessor name
 // prefix are optional.  The suffix directs the generation of getter and