Remove dart backend

tool/test.sh

 #!/bin/bash
 set -e # bail on error
 
 function fail {
   echo -e "Some tests failed"
   return 1
 }
 
 # Arguments passed to the diff tool. We exclude:
 #  - *.map files so they aren't compared, as the diff is not human readable.
@@ skipping 28 matching lines @@
 # code coverage.
 unset COVERALLS_TOKEN
 pub run test:test test/all_tests.dart || fail
 
 # validate codegen_test output
 pushd test/codegen/ &> /dev/null
 rm -r actual/dev_compiler/ actual/sunflower/dev_compiler
 diff $DIFF_ARGS > /dev/null || show_diff
 popd &> /dev/null
 
-# validate dart_codegen_test output
-pushd test/dart_codegen/ &> /dev/null
-diff $DIFF_ARGS > /dev/null || show_diff
-popd &> /dev/null
-
 # run self host and analyzer after other tests, because they're ~seconds to run.
 pub run test:test test/checker/self_host_test.dart || fail
 
 # Run analyzer on bin/devc.dart, as it includes most of the code we care about
 # via transitive dependencies. This seems to be the only fast way to avoid
 # repeated analysis of the same code.
 # TODO(jmesserly): ideally we could do test/all_tests.dart, but
 # dart_runtime_test.dart creates invalid generic type instantiation AA.
 echo "Running dartanalyzer to check for errors/warnings/hints..."
 dartanalyzer --fatal-warnings --package-warnings bin/devc.dart | (! grep $PWD) \
@@ skipping 10 matching lines @@
 # The formatter ignores:
 #   * local files that have never been added to git,
 #   * subdirectories of test/ and tool/, unless explicitly added. Those dirs
 #     contain a lot of generated or external source we should not reformat.
 (files=`git ls-files 'bin/*.dart' 'lib/*.dart' test/*.dart test/checker/*.dart \
   tool/*.dart | grep -v lib/src/js/`; git status -s $files | grep -q . \
   && echo "Did not run the formatter, please commit edited files first." \
   || (echo "Running dart formatter" ; pub run dart_style:format -w $files))
 
 echo -e "All tests pass"