Extend compiler API to support multiple outputs.

dart/sdk/lib/_internal/compiler/implementation/js_backend/emitter.dart

Index: dart/sdk/lib/_internal/compiler/implementation/js_backend/emitter.dart
diff --git a/dart/sdk/lib/_internal/compiler/implementation/js_backend/emitter.dart b/dart/sdk/lib/_internal/compiler/implementation/js_backend/emitter.dart
index 98bfa720934716c12d4ea9fa406c94f540558669..c251ad4780724602b0524c52d2bb8841ccfd3af5 100644
--- a/dart/sdk/lib/_internal/compiler/implementation/js_backend/emitter.dart
+++ b/dart/sdk/lib/_internal/compiler/implementation/js_backend/emitter.dart
@@ -2165,11 +2165,9 @@ if (typeof document !== 'undefined' && document.readyState !== 'complete') {
       if (generateSourceMap) {
         SourceFile compiledFile = new SourceFile(null, compiler.assembledCode);
         String sourceMap = buildSourceMap(mainBuffer, compiledFile);
-        // TODO(podivilov): We should find a better way to return source maps to
-        // compiler. Using diagnostic handler for that purpose is a temporary
-        // hack.
-        compiler.reportDiagnostic(
-            null, sourceMap, new api.Diagnostic(-1, 'source map'));
+        compiler.outputProvider('', 'js.map')
+            ..add(sourceMap)
+            ..close();

[ngeoffray, 2013/01/10 12:15:21]

Would that look nicer if it was just below the '.' of line 2168?

[ahe, 2013/01/25 15:50:09]

It might look nicer, but it I think it would be confusing. One might think that
we called "add" and "close" on "compiler", not the result of
"compiler.outputProvider('', 'js.map')"

       }
     });
     return compiler.assembledCode;