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

lib/compiler/implementation/ssa/optimize.dart

Index: lib/compiler/implementation/ssa/optimize.dart
===================================================================
--- lib/compiler/implementation/ssa/optimize.dart	(revision 6835)
+++ lib/compiler/implementation/ssa/optimize.dart	(working copy)
@@ -178,9 +178,9 @@
       Element element = type.lookupMember(node.name);
       // TODO(ngeoffray): Also fold if it's a getter or variable.
       if (element != null && element.isFunction()) {
-        FunctionElement method = element;
-        FunctionParameters parameters = method.computeParameters(compiler);
-        if (node.selector.applies(parameters)) {
+        if (node.selector.applies(element, compiler)) {
+          FunctionElement method = element;
+          FunctionParameters parameters = method.computeParameters(compiler);
           if (parameters.optionalParameterCount == 0) {
             node.element = element;
           }