Add IR nodes needed for deferred loading.

pkg/kernel/binary.md

Index: pkg/kernel/binary.md
diff --git a/pkg/kernel/binary.md b/pkg/kernel/binary.md
index a287dd6be83b9b2884a61d04c12ab347a3fb7af5..e676b1f91d7ad123250c3b2511db03c4d4d2a9d7 100644
--- a/pkg/kernel/binary.md
+++ b/pkg/kernel/binary.md
@@ -175,11 +175,22 @@ type Library {
   StringReference importUri;
   // An absolute path URI to the .dart file from which the library was created.
   UriReference fileUri;
+  List<DeferredImport> deferredImports;
   List<Class> classes;
   List<Field> fields;
   List<Procedure> procedures;
 }
 
+type DeferredImport {
+  LibraryReference importedLibrary;
+  StringReference name;
+}
+
+type DeferredImportReference {
+  // Index into deferredImports in the enclosing Library.
+  UInt index;
+}
+
 abstract type Node {
   Byte tag;
 }
@@ -664,6 +675,16 @@ type Let extends Expression {
   Expression body;
 }
 
+type LoadLibrary extends Expression {
+  Byte tag = 14;
+  DeferredImportReference import;
+}
+
+type CheckLibraryIsLoaded extends Expression {
+  Byte tag = 13;
+  DeferredImportReference import;
+}
+
 abstract type Statement extends Node {}
 
 type InvalidStatement extends Statement {