Add support for profile-based startup optimizations.

pkg/compiler/lib/src/dart2js.dart

Index: pkg/compiler/lib/src/dart2js.dart
diff --git a/pkg/compiler/lib/src/dart2js.dart b/pkg/compiler/lib/src/dart2js.dart
index a5a4deba233f91c2b537481f07096f8a108ee19b..c56ea75afba56943d049aa386a5a26c8940bb08d 100644
--- a/pkg/compiler/lib/src/dart2js.dart
+++ b/pkg/compiler/lib/src/dart2js.dart
@@ -403,6 +403,14 @@ Future<api.CompilationResult> compile(List<String> argv) {
     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) {