Patches to support Dart VM patch files in dart2js.

pkg/compiler/lib/src/scanner/scanner_task.dart

Index: pkg/compiler/lib/src/scanner/scanner_task.dart
diff --git a/pkg/compiler/lib/src/scanner/scanner_task.dart b/pkg/compiler/lib/src/scanner/scanner_task.dart
index 3d694a3d7110d4762f94b5764be74e85461665d2..b3c158bc6681ba62b08c87d396dc21830cf31899 100644
--- a/pkg/compiler/lib/src/scanner/scanner_task.dart
+++ b/pkg/compiler/lib/src/scanner/scanner_task.dart
@@ -76,6 +76,17 @@ class ScannerTask extends CompilerTask {
     });
   }
 
+  Token tokenizeUnit(CompilationUnitElement unit) {
+    return measureElement(unit, () {
+      Token tokens = new Scanner(
+          unit.script.file, includeComments: _preserveComments).tokenize();
+      if (_preserveComments) {
+        tokens = processAndStripComments(tokens);
+      }
+      return tokens;
+    });
+  }
+
   Token processAndStripComments(Token currentToken) {
     Token firstToken = currentToken;
     Token prevToken;