Refactor Library/CompilationUnit and how we define local Scope.

lib/compiler/implementation/scanner/scanner_task.dart

Index: lib/compiler/implementation/scanner/scanner_task.dart
diff --git a/lib/compiler/implementation/scanner/scanner_task.dart b/lib/compiler/implementation/scanner/scanner_task.dart
index a1ed5fb6ba1faf9dd96d814c8bd959a64ad8bda7..d3aee92515d299aa958a1754aa431c10c96df67f 100644
--- a/lib/compiler/implementation/scanner/scanner_task.dart
+++ b/lib/compiler/implementation/scanner/scanner_task.dart
@@ -6,15 +6,16 @@ class ScannerTask extends CompilerTask {
   ScannerTask(Compiler compiler) : super(compiler);
   String get name() => 'Scanner';
 
+  void scanLibrary(LibraryElement library) {
+    var compilationUnit = library.entryCompilationUnit;
+    compiler.log("scanning library ${compilationUnit.script.name}");
+    scan(compilationUnit);
+    processScriptTags(library);
+  }
+
   void scan(CompilationUnitElement compilationUnit) {
     measure(() {
-      if (compilationUnit.kind === ElementKind.LIBRARY) {
-        compiler.log("scanning library ${compilationUnit.script.name}");
-      }
       scanElements(compilationUnit);
-      if (compilationUnit.kind === ElementKind.LIBRARY) {
-        processScriptTags(compilationUnit);
-      }
     });
   }
 
@@ -35,7 +36,7 @@ class ScannerTask extends CompilerTask {
     }
 
     LinkBuilder<ScriptTag> imports = new LinkBuilder<ScriptTag>();
-    Uri base = library.script.uri;
+    Uri base = library.uri;
     for (ScriptTag tag in library.tags.reverse()) {
       StringNode argument = tag.argument;
       // TODO(lrn): Support interpolations here. We need access to the
@@ -122,7 +123,7 @@ class ScannerTask extends CompilerTask {
         });
     if (newLibrary) {
       compiler.withCurrentElement(library, () {
-        scan(library);
+        scanLibrary(library);
         compiler.onLibraryLoaded(library, uri);
       });
     }
@@ -130,11 +131,12 @@ class ScannerTask extends CompilerTask {
   }
 
   void importLibrary(LibraryElement library, LibraryElement imported,
-                     ScriptTag tag, [CompilationUnitElement patch]) {
+                     ScriptTag tag,
+                     [CompilationUnitElement patchCompilationUnit]) {
     if (!imported.hasLibraryName()) {
       compiler.withCurrentElement(library, () {
         compiler.reportError(tag === null ? null : tag.argument,
-                             'no #library tag found in ${imported.script.uri}');
+                             'no #library tag found in ${imported.uri}');
       });
     }
     if (tag !== null && tag.prefix !== null) {
@@ -142,8 +144,9 @@ class ScannerTask extends CompilerTask {
           new SourceString(tag.prefix.dartString.slowToString());
       Element e = library.find(prefix);
       if (e === null) {
-        e = new PrefixElement(prefix, library, tag.getBeginToken(), patch);
-        library.define(e, compiler);
+        e = new PrefixElement(prefix, library, tag.getBeginToken(),
+                              patchCompilationUnit);
+        library.addToScope(e, compiler);
       }
       if (e.kind !== ElementKind.PREFIX) {
         compiler.withCurrentElement(e, () {
@@ -170,7 +173,7 @@ class ScannerTask extends CompilerTask {
     } else {
       imported.forEachExport((Element element) {
         compiler.withCurrentElement(element, () {
-          library.define(element, compiler);
+          library.addToScope(element, compiler);
         });
       });
     }