Implement complex super assignment.

tests/language/language_dart2js.status

Index: tests/language/language_dart2js.status
===================================================================
--- tests/language/language_dart2js.status	(revision 19425)
+++ tests/language/language_dart2js.status	(working copy)
@@ -203,7 +203,6 @@
 named_parameters_aggregated_test/05: Fail # Absence of positional parameters before named parameters does not trigger static type warning.
 pseudo_kw_test: Fail # Unexpected token '('
 super_implicit_closure_test: Fail # internal error: super property read not implemented
-super_operator_test: Fail # internal error: super property store not implemented
 switch_label_test: Fail # error: target of continue is not a loop or switch case
 on_catch_malformed_type_test: Fail # Malformed types cause compile-time errors.
 
@@ -322,9 +321,6 @@
 
 assign_top_method_test: Fail
 
-super_operator_index2_test: Fail # Issue 8800
-super_operator_index_test/01: Fail # Issue 8800
-
 [ $compiler == dart2js && $runtime == none ]
 *: Fail, Pass # TODO(ahe): Triage these tests.