Support customizing API (and hence mock) compiler to minify the output.

lib/compiler/implementation/dart_backend/backend.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 DartBackend extends Backend {
   final List<CompilerTask> tasks;
+  final bool minify;
 
   Map<Element, TreeElements> get resolvedElements =>
       compiler.enqueuer.resolution.resolvedElements;
 
-  DartBackend(Compiler compiler)
+  DartBackend(Compiler compiler, this.minify)
       : tasks = <CompilerTask>[],
       super(compiler);
 
   void enqueueHelpers(Enqueuer world) { }
   void codegen(WorkItem work) { }
   void processNativeClasses(Enqueuer world,
                             Collection<LibraryElement> libraries) { }
 
   void assembleProgram() {
     /**
@@ skipping 72 matching lines @@
       collector.collect(element, treeElements);
       if (element is ClassElement) {
         classMembers[element].forEach(makePlaceholders);
       }
     }
     topLevelElements.forEach(makePlaceholders);
 
     // Create renames.
     Map<Node, String> renames = new Map<Node, String>();
     Map<LibraryElement, String> imports = new Map<LibraryElement, String>();
-    renamePlaceholders(compiler, collector, renames, imports);
+    Generator topLevelGenerator =

[Roman, 2012/08/24 07:21:04]

It is weird that generators are defined in renamer.dart, but you use them from
here. It should look better if either:
1) pass minify to renamePlaceholders()
2) or move MinifyingGenerator and ConservativeGenerator to this file.

[Roman, 2012/08/24 07:27:01]

I just thought it would be better to pass the flag, because with my CL there
will be minifying generator for locals too, and it should have different
alphabet, so it would be:
1) pass minify to renamePlacheolders()
2) pass both top-level generator and local generator to renamer

[Anton Muhin, 2012/08/24 08:42:53]

Done.

+        minify ? new MinifyingGenerator('ABCD').generate : conservativeGenerator;

[Roman, 2012/08/24 07:21:04]

80 chars

[Anton Muhin, 2012/08/24 08:42:53]

Now obsolete

On 2012/08/24 07:21:04, Roman wrote:

+    renamePlaceholders(
+        compiler, collector, renames, imports, topLevelGenerator);
 
     // Sort elements.
     final sortedTopLevels = sortElements(topLevelElements);
     final sortedClassMembers = new Map<ClassElement, List<Element>>();
     classMembers.forEach((classElement, members) {
       sortedClassMembers[classElement] = sortElements(members);
     });
 
     final unparser = new Unparser.withRenamer((Node node) => renames[node]);
     compiler.assembledCode = emitCode(
@@ skipping 76 matching lines @@
 
 List<Element> sortElements(Collection<Element> elements) {
   compareElements(e0, e1) {
     int result = compareBy((e) => e.getLibrary().uri.toString())(e0, e1);
     if (result != 0) return result;
     return compareBy((e) => e.position().charOffset)(e0, e1);
   }
 
   return sorted(elements, compareElements);
 }