Revert "Move Compiler.libraries to LibraryLoder."

pkg/dart2js_incremental/lib/caching_compiler.dart

Index: pkg/dart2js_incremental/lib/caching_compiler.dart
diff --git a/pkg/dart2js_incremental/lib/caching_compiler.dart b/pkg/dart2js_incremental/lib/caching_compiler.dart
index 8c4f5bd073072e3487c41cb40ae25634f3775ac4..181f405e3782c877863ff2e997fbf49c3caba00e 100644
--- a/pkg/dart2js_incremental/lib/caching_compiler.dart
+++ b/pkg/dart2js_incremental/lib/caching_compiler.dart
@@ -130,9 +130,15 @@ Compiler reuseCompiler(
     backend
         ..preMirrorsMethodCount = 0;
 
-    compiler.libraryLoader.reset(reuseLibrary: (LibraryElement library) {
-      return library.isPlatformLibrary ||
-             (packagesAreImmutable && library.isPackageLibrary);
+    Map libraries = new Map.from(compiler.libraries);
+    compiler.libraries.clear();
+    compiler.libraryLoader.reset();
+    libraries.forEach((String uri, LibraryElement library) {
+      if (library.isPlatformLibrary ||
+          (packagesAreImmutable && library.isPackageLibrary)) {
+        compiler.libraries[uri] = library;
+        compiler.libraryLoader.reuseLibrary(library);
+      }
     });
   }
   oldTag.makeCurrent();