Load builtin helper libraries on demand.

sdk/lib/_internal/compiler/implementation/compiler.dart

Index: sdk/lib/_internal/compiler/implementation/compiler.dart
diff --git a/sdk/lib/_internal/compiler/implementation/compiler.dart b/sdk/lib/_internal/compiler/implementation/compiler.dart
index 88d35c5b5e09c04ad7913bb54136a2fed13d1890..866bb33ca1a9c9cc6b8ee4b846720659b1c6f5db 100644
--- a/sdk/lib/_internal/compiler/implementation/compiler.dart
+++ b/sdk/lib/_internal/compiler/implementation/compiler.dart
@@ -206,7 +206,7 @@ abstract class Backend {
 
   void registerStaticUse(Element element, Enqueuer enqueuer) {}
 
-  void onLibraryScanned(LibraryElement library, Uri uri) {}
+  void onLibraryLoaded(LibraryElement library, Uri uri) {}
 
   void registerMetadataInstantiatedType(DartType type, TreeElements elements) {}
   void registerMetadataStaticUse(Element element) {}
@@ -704,7 +704,7 @@ abstract class Compiler implements DiagnosticListener {
    * This method is called before [library] import and export scopes have been
    * set up.
    */
-  void onLibraryScanned(LibraryElement library, Uri uri) {
+  void onLibraryLoaded(LibraryElement library, Uri uri) {
     if (dynamicClass != null) {
       // When loading the built-in libraries, dynamicClass is null. We
       // take advantage of this as core imports js_helper and sees [dynamic]
@@ -726,7 +726,15 @@ abstract class Compiler implements DiagnosticListener {
       deferredLibraryClass =
           findRequiredElement(library, const SourceString('DeferredLibrary'));
     }

[ngeoffray, 2013/08/15 19:13:02]

Nit: Keep the else/if syntax.

[zarah, 2013/08/28 10:20:13]

Done.

-    backend.onLibraryScanned(library, uri);
+
+    if (isolateHelperLibrary == null
+        && (uri == new Uri(scheme: 'dart', path: '_isolate_helper'))) {
+      isolateHelperLibrary = scanBuiltinLibrary('_isolate_helper');
+    } else if (foreignLibrary == null
+        && (uri == new Uri(scheme: 'dart', path: '_foreign_helper'))) {

[ngeoffray, 2013/08/15 19:13:02]

Nit: '&&' at the same indentation as foreignLibrary === null

[zarah, 2013/08/28 10:20:13]

Done.

+      foreignLibrary = scanBuiltinLibrary('_foreign_helper');
+    }
+    backend.onLibraryLoaded(library, uri);
   }
 
   Element findRequiredElement(LibraryElement library, SourceString name) {
@@ -835,9 +843,6 @@ abstract class Compiler implements DiagnosticListener {
   void scanBuiltinLibraries() {
     jsHelperLibrary = scanBuiltinLibrary('_js_helper');
     interceptorsLibrary = scanBuiltinLibrary('_interceptors');

[ngeoffray, 2013/08/15 19:13:02]

What about those two? Do you plan on moving them? Are there some restrictions
that prevent moving them?

[zarah, 2013/08/28 10:20:13]

The jsHelperLibrary is used just below and the interceptorsLibrary is used in
findInterceptor() so they cannot be moved unfortunately.

-    foreignLibrary = scanBuiltinLibrary('_foreign_helper');
-    isolateHelperLibrary = scanBuiltinLibrary('_isolate_helper');
-
     assertMethod = jsHelperLibrary.find(const SourceString('assertHelper'));
     identicalFunction = coreLibrary.find(const SourceString('identical'));