First step towards having patch files for generic libraries.

lib/compiler/implementation/scanner/scanner_task.dart

 // 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.
 
 class ScannerTask extends CompilerTask {
   ScannerTask(Compiler compiler) : super(compiler);
   String get name() => 'Scanner';
 
   void scan(CompilationUnitElement compilationUnit) {
     measure(() {
@@ skipping 62 matching lines @@
     // better way to access "dart:core".
     bool implicitlyImportCoreLibrary = compiler.coreLibrary !== null;
     for (ScriptTag tag in imports.toLink()) {
       // Now that we have processed all the source tags, it is safe to
       // start loading other libraries.
       StringNode argument = tag.argument;
       Uri resolved = base.resolve(argument.dartString.slowToString());
       if (resolved.toString() == "dart:core") {
         implicitlyImportCoreLibrary = false;
       }
-      importLibrary(library, loadLibrary(resolved, argument), tag);
+      LibraryElement importedLibrary = loadLibrary(resolved, argument);
+      importLibrary(library, importedLibrary, tag);
+      if (resolved.scheme == "dart") {
+        compiler.patchDartLibrary(importedLibrary, resolved.path);
+      }
     }
     if (implicitlyImportCoreLibrary) {
       importLibrary(library, compiler.coreLibrary, null);
     }
   }
 
   void scanElements(CompilationUnitElement compilationUnit) {
     Script script = compilationUnit.script;
     Token tokens;
     try {
@@ skipping 106 matching lines @@
   static final int RESOURCE = 4;
 
   /** Next state. */
   static final List<int> NEXT =
       const <int>[NO_TAG_SEEN,
                   IMPORT, // Only one library tag is allowed.
                   IMPORT,
                   SOURCE,
                   RESOURCE];
 }