Add option for outputting a deferred loading mapping.

pkg/compiler/lib/src/js_emitter/old_emitter/emitter.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 part of dart2js.js_emitter;
 
 
 class OldEmitter implements Emitter {
   final Compiler compiler;
   final CodeEmitterTask task;
@@ skipping 1715 matching lines @@
     }
 
     // Constants in checked mode call into RTI code to set type information
     // which may need getInterceptor (and one-shot interceptor) methods, so
     // we have to make sure that [emitGetInterceptorMethods] and
     // [emitOneShotInterceptors] have been called.
     emitCompileTimeConstants(mainBuffer, mainOutputUnit);
 
     emitDeferredBoilerPlate(mainBuffer, deferredLoadHashes);
 
+    if (compiler.deferredMapUri != null) {
+      outputDeferredMap();
+    }
+
     // Static field initializations require the classes and compile-time
     // constants to be set up.
     emitStaticNonFinalFieldInitializations(mainBuffer, mainOutputUnit);
     interceptorEmitter.emitInterceptedNames(mainBuffer);
     interceptorEmitter.emitMapTypeToInterceptor(mainBuffer);
     emitLazilyInitializedStaticFields(mainBuffer);
 
     mainBuffer.writeln();
     mainBuffer.write(nativeBuffer);
 
@@ skipping 517 matching lines @@
     SourceFile compiledFile = new StringSourceFile(null, code);
     SourceMapBuilder sourceMapBuilder =
             new SourceMapBuilder(sourceMapUri, fileUri, compiledFile);
     buffer.forEachSourceLocation(sourceMapBuilder.addMapping);
     String sourceMap = sourceMapBuilder.build();
     compiler.outputProvider(name, 'js.map')
         ..add(sourceMap)
         ..close();
   }
 
+  void outputDeferredMap() {
+    Map mapping = new Map();

[floitsch, 2015/01/05 14:10:38]

types.

[sigurdm, 2015/01/05 15:23:08]

I changed it to Map<String, dynamic> If we want the comment to stay, then it
cannot get more precise.

+    // Json does not support comments, so we embed the explanation in the
+    // data.
+    mapping["_comment"] = "This mapping shows which compiled `.js` files are "
+        "needed for a given deferred library import.";
+    mapping.addAll(compiler.deferredLoadTask.deferredMap());
+    compiler.outputProvider(compiler.deferredMapUri.path, 'deferred_map')
+        ..add(const JsonEncoder.withIndent("  ").convert(mapping))
+        ..close();
+  }
+
   void invalidateCaches() {
     if (!compiler.hasIncrementalSupport) return;
     if (cachedElements.isEmpty) return;
     for (Element element in compiler.enqueuer.codegen.newlyEnqueuedElements) {
       if (element.isInstanceMember) {
         cachedClassBuilders.remove(element.enclosingClass);
 
         nativeEmitter.cachedBuilders.remove(element.enclosingClass);
 
       }
     }
   }
 }