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

lib/compiler/implementation/dart_backend/backend.dart

Index: lib/compiler/implementation/dart_backend/backend.dart
diff --git a/lib/compiler/implementation/dart_backend/backend.dart b/lib/compiler/implementation/dart_backend/backend.dart
index 173fdefc00c4081cf887d3f47e6628af542f47a6..b2532aac061bcdf382a635803e192a812f8a2249 100644
--- a/lib/compiler/implementation/dart_backend/backend.dart
+++ b/lib/compiler/implementation/dart_backend/backend.dart
@@ -4,11 +4,12 @@
 
 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);
 
@@ -101,7 +102,10 @@ class DartBackend extends Backend {
     // 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);