Refactor and simplify the dart2dart renamer.

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

Index: sdk/lib/_internal/compiler/implementation/dart_backend/backend.dart
diff --git a/sdk/lib/_internal/compiler/implementation/dart_backend/backend.dart b/sdk/lib/_internal/compiler/implementation/dart_backend/backend.dart
index 92c0156325d3392253a5ee2faa22db0d9f4d731c..82bbf9b1aa87ed5b307652697dfd13ebb2be4325 100644
--- a/sdk/lib/_internal/compiler/implementation/dart_backend/backend.dart
+++ b/sdk/lib/_internal/compiler/implementation/dart_backend/backend.dart
@@ -23,11 +23,11 @@ class DartBackend extends Backend {
   final bool stripAsserts;
   // TODO(antonm): make available from command-line options.
   final bool outputAst = false;
-  final Map<Node, String> renames;
-  final Map<LibraryElement, String> imports;
   final Map<ClassNode, List<Node>> memberNodes;
   Map<Element, LibraryElement> reexportingLibraries;
 
+  PlaceholderRenamer placeholderRenamer;
+
   // TODO(zarah) Maybe change this to a command-line option.
   // Right now, it is set by the tests.
   bool useMirrorHelperLibrary = false;
@@ -105,8 +105,6 @@ class DartBackend extends Backend {
 
   DartBackend(Compiler compiler, List<String> strips)
       : tasks = <CompilerTask>[],
-        renames = new Map<Node, String>(),
-        imports = new Map<LibraryElement, String>(),
         memberNodes = new Map<ClassNode, List<Node>>(),
         reexportingLibraries = <Element, LibraryElement>{},
         forceStripTypes = strips.indexOf('types') != -1,
@@ -396,14 +394,15 @@ class DartBackend extends Backend {
     bool shouldCutDeclarationTypes = forceStripTypes
         || (compiler.enableMinification
             && isSafeToRemoveTypeDeclarations(classMembers));
-    renamePlaceholders(
-        compiler, collector, renames, imports,
-        fixedMemberNames, reexportingLibraries,
-        shouldCutDeclarationTypes,
-        uniqueGlobalNaming: useMirrorHelperLibrary);
+
+    placeholderRenamer =
+        new PlaceholderRenamer(compiler, fixedMemberNames, reexportingLibraries,
+            cutDeclarationTypes: shouldCutDeclarationTypes);
+
+    placeholderRenamer.computeRenamings(collector);
 
     // Sort elements.
-    final sortedTopLevels = sortElements(topLevelElements);
+    final List<Element> sortedTopLevels = sortElements(topLevelElements);
     final sortedClassMembers = new Map<ClassElement, List<Element>>();
     classMembers.forEach((classElement, members) {
       sortedClassMembers[classElement] = sortElements(members);
@@ -430,7 +429,7 @@ class DartBackend extends Backend {
       return;
     }
 
-    final topLevelNodes = <Node>[];
+    final List<Node> topLevelNodes = <Node>[];
     for (final element in sortedTopLevels) {
       topLevelNodes.add(elementAsts[element].ast);
       if (element.isClass && !element.isMixinApplication) {
@@ -443,18 +442,34 @@ class DartBackend extends Backend {
     }
 
     if (useMirrorHelperLibrary) {
-      mirrorRenamer.addRenames(renames, topLevelNodes, collector);
+      mirrorRenamer.addRenames(placeholderRenamer.renames,
+                               topLevelNodes, collector);
     }
 
-    final unparser = new EmitterUnparser(renames, stripTypes: forceStripTypes,
-        minify: compiler.enableMinification);
-    emitCode(unparser, imports, topLevelNodes, memberNodes);
-    String assembledCode = unparser.result;
-    compiler.outputProvider('', 'dart')
-        ..add(assembledCode)
-        ..close();
-    compiler.assembledCode = assembledCode;
+    final unparser = new EmitterUnparser(placeholderRenamer.renames,
+                                         stripTypes: forceStripTypes,
+                                         minify: compiler.enableMinification);
+    for(LibraryElement library in placeholderRenamer.platformImports) {
+      if (library.isPlatformLibrary && !library.isInternalLibrary) {
+        unparser.unparseImportTag(library.canonicalUri.toString());
+      }
+    }
+    for (int i = 0; i < sortedTopLevels.length; i++) {
+      Element element = sortedTopLevels[i];
+      Node node = topLevelNodes[i];
+      if (node is ClassNode) {
+        // TODO(smok): Filter out default constructors here.
+        unparser.unparseClassWithBody(node, memberNodes[node]);
+      } else {
+        unparser.unparse(node);
+      }
+      unparser.newline();
+    }
 
+    compiler.assembledCode = unparser.result;
+    compiler.outputProvider("", "dart")
+         ..add(compiler.assembledCode)
+         ..close();
     // Output verbose info about size ratio of resulting bundle to all
     // referenced non-platform sources.
     logResultBundleSizeInfo(topLevelElements);