Introduce typed selectors to do better tree shaking based on calls on 'this'. Getters and setters w…

lib/compiler/implementation/emitter.dart

Index: lib/compiler/implementation/emitter.dart
===================================================================
--- lib/compiler/implementation/emitter.dart	(revision 6835)
+++ lib/compiler/implementation/emitter.dart	(working copy)
@@ -168,9 +168,8 @@
                          StringBuffer buffer) {
     Set<Selector> selectors = compiler.universe.invokedNames[member.name];
     if (selectors == null) return;
-    FunctionParameters parameters = member.computeParameters(compiler);
     for (Selector selector in selectors) {
-      if (!selector.applies(parameters)) continue;
+      if (!selector.applies(member, compiler)) continue;
       addParameterStub(member, attachTo, buffer, selector);
     }
   }