dart2js cps: Use 'this' instead of receiver when possible.

tests/lib/lib.status

 # 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.
 
 [ $unchecked ]
 mirrors/redirecting_factory_different_type_test: SkipByDesign # Tests type checks.
 
 [ $compiler == dart2js ]
 async/schedule_microtask6_test: RuntimeError # global error handling is not supported. Issue 5958
 
@@ skipping 318 matching lines @@
 convert/streamed_conversion_json_utf8_decode_test: Skip  # Verification not yet implemented.
 
 [ $runtime == vm && $mode == debug && $builder_tag == asan ]
 mirrors/immutable_collections_test: SkipSlow  # Timeout.
 convert/streamed_conversion_json_utf8_decode_test: Skip  # Timeout.
 
 [ $compiler == dart2js && $cps_ir ]
 async/async_await_zones_test: Crash # (await for(var x in bar().take(100)){sum+= x;}): await for
 async/stream_empty_test: RuntimeError # $async$temp1.runTest_unreachable is not a function
 async/stream_iterator_test: Crash # (Stream createCancel...  cannot handle sync*/async* functions
-convert/ascii_test: RuntimeError # this.get$length is not a function
 convert/json_pretty_test: Crash # (static Iterable<Str...  cannot handle sync*/async* functions
-convert/latin1_test: RuntimeError # this.get$length is not a function
 convert/line_splitter_test: Crash # (static Iterable<Str...  cannot handle sync*/async* functions
 mirrors/abstract_class_test/00: Crash # (static Iterable<Str...  cannot handle sync*/async* functions
 mirrors/abstract_class_test/none: Crash # (static Iterable<Str...  cannot handle sync*/async* functions
 mirrors/abstract_test: Crash # (static Iterable<Str...  cannot handle sync*/async* functions
 mirrors/accessor_cache_overflow_test: Crash # (static Iterable<Str...  cannot handle sync*/async* functions
 mirrors/array_tracing2_test: Crash # (static Iterable<Str...  cannot handle sync*/async* functions
 mirrors/array_tracing_test: Crash # (static Iterable<Str...  cannot handle sync*/async* functions
 mirrors/basic_types_in_dart_core_test: Crash # (static Iterable<Str...  cannot handle sync*/async* functions
 mirrors/circular_factory_redirection_test/none: Crash # (static Iterable<Str...  cannot handle sync*/async* functions
 mirrors/class_declarations_test/01: Crash # (static Iterable<Str...  cannot handle sync*/async* functions
@@ skipping 205 matching lines @@
 mirrors/type_variable_is_static_test: Crash # (static Iterable<Str...  cannot handle sync*/async* functions
 mirrors/type_variable_owner_test/01: Crash # (static Iterable<Str...  cannot handle sync*/async* functions
 mirrors/type_variable_owner_test/none: Crash # (static Iterable<Str...  cannot handle sync*/async* functions
 mirrors/typearguments_mirror_test: Crash # (static Iterable<Str...  cannot handle sync*/async* functions
 mirrors/typedef_deferred_library_test: RuntimeError # G.loadLibrary is not a function
 mirrors/typedef_metadata_test: Crash # (static Iterable<Str...  cannot handle sync*/async* functions
 mirrors/typedef_reflected_type_test/01: Crash # (static Iterable<Str...  cannot handle sync*/async* functions
 mirrors/typedef_reflected_type_test/none: Crash # (static Iterable<Str...  cannot handle sync*/async* functions
 mirrors/unnamed_library_test: Crash # (static Iterable<Str...  cannot handle sync*/async* functions
 mirrors/variable_is_const_test/none: Crash # (static Iterable<Str...  cannot handle sync*/async* functions
-typed_data/typed_data_list_test: RuntimeError # this.get$length is not a function