Support browser caching using hashes in serverMode (fixes #93, fixes #92)

lib/src/codegen/js_codegen.dart

Index: lib/src/codegen/js_codegen.dart
diff --git a/lib/src/codegen/js_codegen.dart b/lib/src/codegen/js_codegen.dart
index 028a5152f56f0ae9ab30c4dd018c910a93fdb44d..16cd725d030d0a2863283dcc09c4c6890a6d6770 100644
--- a/lib/src/codegen/js_codegen.dart
+++ b/lib/src/codegen/js_codegen.dart
@@ -1926,7 +1926,7 @@ class JSGenerator extends CodeGenerator {
   JSGenerator(String outDir, Uri root, TypeRules rules, this.options)
       : super(outDir, root, rules);
 
-  void generateLibrary(Iterable<CompilationUnit> units, LibraryInfo info,
+  String generateLibrary(Iterable<CompilationUnit> units, LibraryInfo info,
       CheckerReporter reporter) {
     JS.Program jsTree =
         new JSCodegenVisitor(info, rules).generateLibrary(units, reporter);
@@ -1941,10 +1941,14 @@ class JSGenerator extends CodeGenerator {
           printer, path.dirname(outputPath)), jsTree);
       printer.add('//# sourceMappingURL=$outFilename.map');
       // Write output file and source map
-      new File(outputPath).writeAsStringSync(printer.text);
+      var text = printer.text;
+      new File(outputPath).writeAsStringSync(text);
       new File('$outputPath.map').writeAsStringSync(printer.map);
+      return computeHash(text);
     } else {
-      new File(outputPath).writeAsStringSync(jsNodeToString(jsTree));
+      var text = jsNodeToString(jsTree);
+      new File(outputPath).writeAsStringSync(text);
+      return computeHash(text);
     }
   }
 }