Add support for profile-based startup optimizations.

pkg/compiler/lib/src/dart2js.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library dart2js.cmdline;
 
 import 'dart:async' show Future;
 import 'dart:convert' show UTF8, LineSplitter;
 import 'dart:io' show exit, File, FileMode, Platform, stdin, stderr;
 
@@ skipping 385 matching lines @@
     new OptionHandler('--enable-enum', (_) {
       hints.add("Option '--enable-enum' is no longer needed. "
           "Enums are supported by default.");
     }),
     new OptionHandler(Flags.allowNativeExtensions, setAllowNativeExtensions),
     new OptionHandler(Flags.generateCodeWithCompileTimeErrors, passThrough),
     new OptionHandler(Flags.useMultiSourceInfo, passThrough),
     new OptionHandler(Flags.useNewSourceInfo, passThrough),
     new OptionHandler(Flags.testMode, passThrough),
 
+    // Experimental features.
+    // We don't provide documentation for these yet.
+    // TODO(29574): provide documentation when this feature is supported.
+    // TODO(29574): provide a warning/hint/error, when profile-based data is
+    // used without `--fast-startup`.
+    new OptionHandler(Flags.experimentalTrackAllocations, passThrough),
+    new OptionHandler("${Flags.experimentalAllocationsPath}=.+", passThrough),
+
     // The following three options must come last.
     new OptionHandler('-D.+=.*', addInEnvironment),
     new OptionHandler('-.*', (String argument) {
       helpAndFail("Unknown option '$argument'.");
     }),
     new OptionHandler('.*', (String argument) {
       arguments.add(nativeToUriPath(argument));
     })
   ];
 
@@ skipping 622 matching lines @@
   @override
   void add(String event) {
     sb.write(event);
   }
 
   @override
   void close() {
     // Do nothing.
   }
 }