Add CompilationUnit abstraction for tracking "project files".

dart/site/try/src/compilation.dart

Index: dart/site/try/src/compilation.dart
diff --git a/dart/site/try/src/compilation.dart b/dart/site/try/src/compilation.dart
index 9228ed417118164ae31b596b67b7e8e0fb7e91c2..b5da4dcafea23468ba7940dff5797a8506518d0d 100644
--- a/dart/site/try/src/compilation.dart
+++ b/dart/site/try/src/compilation.dart
@@ -11,7 +11,8 @@ import 'dart:html' show
     IFrameElement,
     MessageEvent,
     Url,
-    Worker;
+    Worker,
+    window;
 
 import 'dart:async' show
     Timer;
@@ -22,7 +23,6 @@ import 'dart:isolate' show
 
 import 'editor.dart' show
     addDiagnostic,
-    currentSource,
     isMalformedInput;
 
 import 'run.dart' show
@@ -63,6 +63,13 @@ const String PRIVATE_SCHEME = 'org-trydart';
 SendPort compilerPort;
 Timer compilerTimer;
 
+// TODO(ahe): Remove this.
+String get currentSource => window.localStorage['currentSource'];
+
+void set currentSource(String text) {
+  window.localStorage['currentSource'] = text;
+}
+
 void scheduleCompilation() {
   if (compilationPaused) return;
   if (compilerTimer != null) {