chore(build): tighten up code size check now that regression is fixed

Our code size SLA is 100kb gzipped and 300kb minified. Our target is 10kb gzipped.

We are currently under 90kb gzipped. Let's keep it that way while looking for ways to improve the situation further. We're not <300kb minified yet, so we should be stricter here too.

Closes angular#5896

Author: yjbanov

gulpfile.js

@@ -638,7 +638,7 @@ gulp.task('test.unit.dart', function(done) {
 // This test will fail if the size of our hello_world app goes beyond one of
 // these values when compressed at the specified level.
 // Measure in bytes.
-var _DART_PAYLOAD_SIZE_LIMITS = {'uncompressed': 375 * 1024, 'gzip level=6': 105 * 1024};
+var _DART_PAYLOAD_SIZE_LIMITS = {'uncompressed': 320 * 1024, 'gzip level=6': 90 * 1024};
 gulp.task('test.payload.dart/ci', function(done) {
   runSequence('build/packages.dart', '!pubget.payload.dart', '!pubbuild.payload.dart',
               '!checkAndReport.payload.dart', done);