DDC: mostly incremental compilation, fixes #223

tool/patch_sdk.dart

Index: tool/patch_sdk.dart
diff --git a/tool/patch_sdk.dart b/tool/patch_sdk.dart
index e8bc7409ef59495f084ba5790cf062e86ac397de..1b6dad29b4b903f22d6fa8b56a4a8435575ebb71 100755
--- a/tool/patch_sdk.dart
+++ b/tool/patch_sdk.dart
@@ -15,8 +15,8 @@ import 'package:analyzer/src/generated/sdk.dart';
 import 'package:path/path.dart' as path;
 
 void main(List<String> argv) {
+  var self = path.relative(path.fromUri(Platform.script));
   if (argv.length < 2) {
-    var self = path.relative(path.fromUri(Platform.script));
     var toolDir = path.relative(path.dirname(path.fromUri(Platform.script)));
 
     var inputExample = path.join(toolDir, 'input_sdk');
@@ -32,6 +32,7 @@ void main(List<String> argv) {
     print('\$ $self $inputExample $outExample');
     exit(1);
   }
+  var selfLastModify = new File(self).lastModifiedSync().millisecondsSinceEpoch;
 
   var input = argv[0];
   var sdkLibIn = path.join(input, 'lib');
@@ -102,6 +103,9 @@ void main(List<String> argv) {
             patchFile.lastModifiedSync().millisecondsSinceEpoch);
       }
 
+      // If the patch_sdk itself was modified, take that into account.
+      inputModifyTime = math.max(inputModifyTime, selfLastModify);
+
       // Compute output paths
       outPaths = outPaths
           .map((p) => path.join(sdkOut, path.relative(p, from: sdkLibIn)))