Add "load from .dill" file capability and run a white-box test.

pkg/compiler/lib/src/compiler.dart

Index: pkg/compiler/lib/src/compiler.dart
diff --git a/pkg/compiler/lib/src/compiler.dart b/pkg/compiler/lib/src/compiler.dart
index 94666231d090e22269a6dd7eb8e7849f6b55808c..c9ebbf1755d0208bd51aeed5c36b304a34c2508f 100644
--- a/pkg/compiler/lib/src/compiler.dart
+++ b/pkg/compiler/lib/src/compiler.dart
@@ -44,6 +44,7 @@ import 'environment.dart';
 import 'id_generator.dart';
 import 'io/source_information.dart' show SourceInformation;
 import 'js_backend/backend.dart' show JavaScriptBackend;
+import 'kernel/world_builder.dart' show KernelWorldBuilder;
 import 'library_loader.dart'
     show
         ElementScanner,
@@ -114,6 +115,11 @@ abstract class Compiler {
 
   List<Uri> librariesToAnalyzeWhenRun;
 
+  /// Object holding the correspondence between Kernel IR and their
+  /// corresponding K/JElements. Only (currently) used when used in conjunction
+  /// with --use-kernel and --read-dill flags.
+  KernelWorldBuilder kernelWorldBuilder;
+
   ResolvedUriTranslator get resolvedUriTranslator;
 
   LibraryElement mainApp;
@@ -212,6 +218,7 @@ abstract class Compiler {
       serialization = new SerializationTask(this),
       patchParser = new PatchParserTask(this),
       libraryLoader = new LibraryLoaderTask(
+          options.loadFromDill,
           resolvedUriTranslator,
           options.compileOnly
               ? new _NoScriptLoader(this)
@@ -348,8 +355,8 @@ abstract class Compiler {
         }
       }
       String importChain = compactImportChain.map((CodeLocation codeLocation) {
-        return codeLocation
-            .relativize(loadedLibraries.rootLibrary.canonicalUri);
+        return codeLocation.relativize(
+            (loadedLibraries.rootLibrary as LibraryElement).canonicalUri);
       }).join(' => ');
 
       if (!importChains.contains(importChain)) {
@@ -381,7 +388,8 @@ abstract class Compiler {
   /// The method returns a [Future] allowing for the loading of additional
   /// libraries.
   LoadedLibraries processLoadedLibraries(LoadedLibraries loadedLibraries) {
-    loadedLibraries.forEachLibrary((LibraryElement library) {
+    kernelWorldBuilder = libraryLoader.worldBuilder;
+    loadedLibraries.forEachLibrary((LibraryEntity library) {
       backend.setAnnotations(library);
     });