First pass at asynchronous input loading in dart2js.

sdk/lib/_internal/compiler/samples/leap/leap_leg.dart

Index: sdk/lib/_internal/compiler/samples/leap/leap_leg.dart
diff --git a/sdk/lib/_internal/compiler/samples/leap/leap_leg.dart b/sdk/lib/_internal/compiler/samples/leap/leap_leg.dart
index 137c236e0a00e251dc7c79cdde190380c0e05810..1735f8502efc283563608c6ffd08e31c8023dd0e 100644
--- a/sdk/lib/_internal/compiler/samples/leap/leap_leg.dart
+++ b/sdk/lib/_internal/compiler/samples/leap/leap_leg.dart
@@ -125,6 +125,7 @@ class Runner {
 
   String init() {
     Stopwatch sw = new Stopwatch()..start();
+    // TODO(rnystrom): Handle future.

[Bob Nystrom, 2013/06/26 01:03:24]

I haven't updated this sample to the new async API yet. Is this still live code?
Do you know how I can test it?

[ahe, 2013/06/26 07:02:00]

Don't bother, it is probably broken anyways. I should delete this when I land
try.dartlang.org as a compiler sample.

[Bob Nystrom, 2013/06/27 00:38:18]

That's what I figured. Updated the TODOs to explain more.

     compiler.scanBuiltinLibraries();
     sw.stop();
     return 'Scanned core libraries in ${sw.elapsedMilliseconds}ms';
@@ -221,10 +222,12 @@ class LeapCompiler extends Compiler {
 
   String get legDirectory => libDir;
 
+  // TODO(rnystrom): Make return future.
   LibraryElement scanBuiltinLibrary(String path) {
     Uri base = Uri.parse(html.window.location.toString());
     Uri libraryRoot = base.resolve(libDir);
     Uri resolved = libraryRoot.resolve(DART2JS_LIBRARY_MAP[path]);
+    // TODO(rnystrom): Handle future.
     LibraryElement library = scanner.loadLibrary(resolved, null);
     return library;
   }
@@ -237,6 +240,7 @@ class LeapCompiler extends Compiler {
     return compilationUnit.script;
   }
 
+  // TODO(rnystrom): Make return future.
   Script readScript(Uri uri, [ScriptTag node]) {
     String text = "";
     try {