Fix some spelling (#884)

Author: kevmoo

pkgs/cronet_http/example/integration_test/client_test.dart

@@ -35,7 +35,7 @@ Future<void> testClientFromFutureFails() async {
   test('cronet engine future fails', () async {
     final engineFuture = CronetEngine.build(
         cacheMode: CacheMode.disk,
-        storagePath: '/non-existant-path/', // Will cause `build` to throw.
+        storagePath: '/non-existent-path/', // Will cause `build` to throw.
         userAgent: 'Test Agent (Future)');
 
     final client = CronetClient.fromCronetEngineFuture(engineFuture);

pkgs/cupertino_http/CHANGELOG.md

@@ -46,7 +46,7 @@
 
 ## 0.0.6
 
-* Make the number of simulateous connections allowed to the same host
+* Make the number of simultaneous connections allowed to the same host
   configurable.
 * Fixes
   [cupertino_http: Failure calling Dart_PostCObject_DL](https://github.com/dart-lang/http/issues/785).

pkgs/http_client_conformance_tests/lib/src/request_body_streamed_server.dart

@@ -8,7 +8,7 @@ import 'dart:io';
 
 import 'package:stream_channel/stream_channel.dart';
 
-/// Starts an HTTP server that absorbes a request stream of integers and
+/// Starts an HTTP server that absorbs a request stream of integers and
 /// signals the client to quit after 1000 have been received.
 ///
 /// Channel protocol:

pkgs/http_client_conformance_tests/lib/src/request_headers_tests.dart

@@ -35,7 +35,7 @@ void testRequestHeaders(Client client) async {
       await client.get(Uri.http(host, ''), headers: {'FOO': 'BAR'});
 
       final headers = await httpServerQueue.next as Map;
-      // RFC 2616 14.44 states that header field names are case-insensive.
+      // RFC 2616 14.44 states that header field names are case-insensitive.
       // http.Client canonicalizes field names into lower case.
       expect(headers['foo'], ['BAR']);
     });

pkgs/http_client_conformance_tests/lib/src/response_headers_tests.dart

@@ -34,7 +34,7 @@ void testResponseHeaders(Client client) async {
       httpServerChannel.sink.add({'foo': 'BAR'});
 
       final response = await client.get(Uri.http(host, ''));
-      // RFC 2616 14.44 states that header field names are case-insensive.
+      // RFC 2616 14.44 states that header field names are case-insensitive.
       // http.Client canonicalizes field names into lower case.
       expect(response.headers['foo'], 'BAR');
     });