Add full BoringSSL error information to Dart exceptions it throws.

tests/standalone/io/http_proxy_test.dart

 // Copyright (c) 2013, 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.
 
 import "package:crypto/crypto.dart";
 import "package:expect/expect.dart";
 import "package:path/path.dart";
 import "dart:async";
 import "dart:io";
 import 'dart:convert';
@@ skipping 267 matching lines @@
 
   int get port => server.port;
 }
 
 Future<ProxyServer> setupProxyServer({ipV6: false}) {
   ProxyServer proxyServer = new ProxyServer(ipV6: ipV6);
   return proxyServer.start();
 }
 
 testInvalidProxy() {
-  HttpClient client = new HttpClient();
+  HttpClient client = new HttpClient(context: clientContext);
 
   client.findProxy = (Uri uri) => "";
   client.getUrl(Uri.parse("http://www.google.com/test"))
     .catchError((error) {}, test: (e) => e is HttpException);
 
   client.findProxy = (Uri uri) => "XXX";
   client.getUrl(Uri.parse("http://www.google.com/test"))
     .catchError((error) {}, test: (e) => e is HttpException);
 
   client.findProxy = (Uri uri) => "PROXY www.google.com";
   client.getUrl(Uri.parse("http://www.google.com/test"))
     .catchError((error) {}, test: (e) => e is HttpException);
 
   client.findProxy = (Uri uri) => "PROXY www.google.com:http";
   client.getUrl(Uri.parse("http://www.google.com/test"))
     .catchError((error) {}, test: (e) => e is HttpException);
 }
 
 int testDirectDoneCount = 0;
 void testDirectProxy() {
   setupServer(0).then((server) {
-    HttpClient client = new HttpClient();
+    HttpClient client = new HttpClient(context: clientContext);
     List<String> proxy =
         ["DIRECT", " DIRECT ", "DIRECT ;", " DIRECT ; ",
          ";DIRECT", " ; DIRECT ", ";;DIRECT;;"];
 
     client.findProxy = (Uri uri) {
       int index = int.parse(uri.path.substring(1));
       return proxy[index];
     };
 
     for (int i = 0; i < proxy.length; i++) {
@@ skipping 88 matching lines @@
 
 
 int testProxyChainDoneCount = 0;
 void testProxyChain() {
   // Setup two proxy servers having the first using the second as its proxy.
   setupProxyServer().then((proxyServer1) {
   setupProxyServer().then((proxyServer2) {
   proxyServer1.client.findProxy = (_) => "PROXY localhost:${proxyServer2.port}";
 
   setupServer(2, directRequestPaths: ["/4"]).then((server) {
-    HttpClient client = new HttpClient();
+    HttpClient client = new HttpClient(context: clientContext);
 
     List<String> proxy;
     if (Platform.operatingSystem == "windows") {
       proxy =
           ["PROXY localhost:${proxyServer1.port}",
            "PROXY localhost:${proxyServer1.port}; PROXY hede.hule.hest:8080",
            "PROXY localhost:${proxyServer1.port}",
            "PROXY localhost:${proxyServer1.port}",
            "DIRECT",
            "PROXY localhost:${proxyServer1.port}; DIRECT"];
@@ skipping 39 matching lines @@
   });
   });
 }
 
 main() {
   testInvalidProxy();
   testDirectProxy();
   testProxy();
   testProxyChain();
 }