Read platform.dill in the VM.

runtime/vm/bootstrap_nocore.cc

Index: runtime/vm/bootstrap_nocore.cc
diff --git a/runtime/vm/bootstrap_nocore.cc b/runtime/vm/bootstrap_nocore.cc
index b3d7484eab39b8c32dadaf129f2b956551b96c22..44cff902480f0956bebf9f6a0cdeee44af1bbaef 100644
--- a/runtime/vm/bootstrap_nocore.cc
+++ b/runtime/vm/bootstrap_nocore.cc
@@ -86,6 +86,7 @@ RawError* BootstrapFromKernel(Thread* thread, kernel::Program* program) {
     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 < bootstrap_library_count; ++i) {
@@ -104,7 +105,18 @@ RawError* BootstrapFromKernel(Thread* thread, kernel::Program* program) {
     }
   }
 
+  // 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();
 }