Resolve libraries against their canonical URI.

dart/pkg/compiler/lib/src/library_loader.dart

Index: dart/pkg/compiler/lib/src/library_loader.dart
diff --git a/dart/pkg/compiler/lib/src/library_loader.dart b/dart/pkg/compiler/lib/src/library_loader.dart
index 8debbe7c92c3ddc79c02608ea5041816dfd72286..25b5288781eff6ca010471d8278addac13d6c346 100644
--- a/dart/pkg/compiler/lib/src/library_loader.dart
+++ b/dart/pkg/compiler/lib/src/library_loader.dart
@@ -435,23 +435,8 @@ class _LibraryLoaderTask extends CompilerTask implements LibraryLoaderTask {
     });
   }
 
-  /// True if the uris are pointing to a library that is shared between dart2js
-  /// and the core libraries. By construction they must be imported into the
-  /// runtime, and, at the same time, into dart2js. This can lead to
-  /// duplicated imports, like in the docgen.
-  // TODO(johnniwinther): is this necessary, or should we change docgen not
-  //   to include both libraries (compiler and lib) at the same time?
-  bool _isSharedDart2jsLibrary(Uri uri1, Uri uri2) {
-    bool inJsLibShared(Uri uri) {
-      List<String> segments = uri.pathSegments;
-      if (segments.length < 3) return false;
-      if (segments[segments.length - 2] != 'shared') return false;
-      return (segments[segments.length - 3] == 'js_lib');
-    }
-    return inJsLibShared(uri1) && inJsLibShared(uri2);
-  }
-
   void checkDuplicatedLibraryName(LibraryElement library) {
+    if (library.isInternalLibrary) return;
     Uri resourceUri = library.entryCompilationUnit.script.resourceUri;
     LibraryName tag = library.libraryTag;
     LibraryElement existing =
@@ -476,8 +461,7 @@ class _LibraryLoaderTask extends CompilerTask implements LibraryLoaderTask {
     } else if (tag != null) {
       String name = library.getLibraryOrScriptName();
       existing = libraryNames.putIfAbsent(name, () => library);
-      if (!identical(existing, library) &&
-          !_isSharedDart2jsLibrary(resourceUri, existing.canonicalUri)) {
+      if (!identical(existing, library)) {
         compiler.withCurrentElement(library, () {
           compiler.reportWarning(tag.name,
               MessageKind.DUPLICATED_LIBRARY_NAME,
@@ -525,7 +509,7 @@ class _LibraryLoaderTask extends CompilerTask implements LibraryLoaderTask {
   Future registerLibraryFromTag(LibraryDependencyHandler handler,
                                 LibraryElement library,
                                 LibraryDependency tag) {
-    Uri base = library.entryCompilationUnit.script.readableUri;
+    Uri base = library.canonicalUri;
     Uri resolvedUri = base.resolve(tag.uri.dartString.slowToString());
     return createLibrary(handler, library, resolvedUri, tag.uri)
         .then((LibraryElement loadedLibrary) {