Read platform.dill in the VM.

runtime/vm/bootstrap.cc

 // Copyright (c) 2012, 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.
 
 #include "vm/bootstrap.h"
 
 #include "include/dart_api.h"
 
 #include "vm/bootstrap_natives.h"
 #include "vm/class_finalizer.h"
@@ skipping 340 matching lines @@
   // Mark the already-pending classes.  This mark bit will be used to avoid
   // adding classes to the list more than once.
   GrowableObjectArray& pending_classes = GrowableObjectArray::Handle(
       zone, isolate->object_store()->pending_classes());
   dart::Class& pending = dart::Class::Handle(zone);
   for (intptr_t i = 0; i < pending_classes.Length(); ++i) {
     pending ^= pending_classes.At(i);
     pending.set_is_marked_for_parsing();
   }
 
+  // Load the bootstrap libraries in order (see object_store.h).
   Library& library = Library::Handle(zone);
   String& dart_name = String::Handle(zone);
   for (intptr_t i = 0; i < kBootstrapLibraryCount; ++i) {
     ObjectStore::BootstrapLibraryId id = bootstrap_libraries[i].index;
     library = isolate->object_store()->bootstrap_library(id);
     dart_name = library.url();
     for (intptr_t j = 0; j < program->libraries().length(); ++j) {
       kernel::Library* kernel_library = program->libraries()[j];
       kernel::String* uri = kernel_library->import_uri();
       const String& kernel_name = reader.DartSymbol(uri);
       if (kernel_name.Equals(dart_name)) {
         reader.ReadLibrary(kernel_library);
         library.SetLoaded();
         break;
       }
     }
   }
 
+  // Finish bootstrapping, including class finalization.
   Finish(thread, /*from_kernel=*/true);
+
+  // The platform binary may contain other libraries (e.g., dart:_builtin or
+  // dart:io) that will not be bundled with application.  Load them now.
+  reader.ReadProgram();
+
+  // The builtin library should be registered with the VM.
+  dart_name = String::New("dart:_builtin");
+  library = Library::LookupLibrary(thread, dart_name);
+  isolate->object_store()->set_builtin_library(library);
+
   return Error::null();
 }
 #else
 static RawError* BootstrapFromKernel(Thread* thread, kernel::Program* program) {
   UNREACHABLE();
   return Error::null();
 }
 #endif
 
 
@@ skipping 18 matching lines @@
       lib.Register(thread);
       isolate->object_store()->set_bootstrap_library(id, lib);
     }
   }
 
   return (kernel_program == NULL) ? BootstrapFromSource(thread)
                                   : BootstrapFromKernel(thread, kernel_program);
 }
 
 }  // namespace dart