Eliminate multi-callback structure for LibraryLoader.

pkg/compiler/lib/src/kernel/kernel.dart

Index: pkg/compiler/lib/src/kernel/kernel.dart
diff --git a/pkg/compiler/lib/src/kernel/kernel.dart b/pkg/compiler/lib/src/kernel/kernel.dart
index 373c8734c165b1abdf28e61d02682f227a75c0cd..c83bc00b5238993466797a28e1dcd62d67e9443e 100644
--- a/pkg/compiler/lib/src/kernel/kernel.dart
+++ b/pkg/compiler/lib/src/kernel/kernel.dart
@@ -37,6 +37,7 @@ import '../elements/elements.dart'
         MixinApplicationElement,
         TypeVariableElement;
 import '../elements/modelx.dart' show ErroneousFieldElementX;
+import '../library_loader.dart' show LoadedLibraries;
 import '../tree/tree.dart' show FunctionExpression, Node;
 import 'constant_visitor.dart';
 import 'kernel_visitor.dart' show IrFunction, KernelVisitor;
@@ -143,7 +144,9 @@ class Kernel {
   }
 
   Future<ir.Library> loadLibrary(Uri uri) async {

[Siggi Cherem (dart-lang), 2017/03/24 17:40:27]

it appears this method is never called, so we can probably delete it and remove
the dependency above :)

[Emily Fortuna, 2017/03/24 18:30:19]

ah good point!

-    return libraryToIr(await compiler.libraryLoader.loadLibrary(uri));
+    LoadedLibraries libraries = await compiler.libraryLoader.loadLibrary(uri);
+    await compiler.processLoadedLibraries(libraries);
+    return libraryToIr(libraries.rootLibrary);
   }
 
   ir.Library libraryToIr(LibraryElement library) {