Add full BoringSSL error information to Dart exceptions it throws.

tests/standalone/io/http_proxy_advanced_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 272 matching lines @@
   ProxyServer proxyServer = new ProxyServer(ipV6: ipV6);
   return proxyServer.start();
 }
 
 
 int testProxyIPV6DoneCount = 0;
 void testProxyIPV6() {
   setupProxyServer(ipV6: true).then((proxyServer) {
   setupServer(1, directRequestPaths: ["/4"]).then((server) {
   setupServer(1, directRequestPaths: ["/4"], secure: true).then((secureServer) {
-    HttpClient client = new HttpClient();
+    HttpClient client = new HttpClient(context: clientContext);
 
     List<String> proxy = ["PROXY [::1]:${proxyServer.port}"];
     client.findProxy = (Uri uri) {
       // Pick the proxy configuration based on the request path.
       int index = int.parse(uri.path.substring(1));
       return proxy[index];
     };
 
     for (int i = 0; i < proxy.length; i++) {
       test(bool secure) {
@@ skipping 29 matching lines @@
   });
   });
 }
 
 
 int testProxyFromEnviromentDoneCount = 0;
 void testProxyFromEnviroment() {
   setupProxyServer().then((proxyServer) {
   setupServer(1).then((server) {
   setupServer(1, secure: true).then((secureServer) {
-    HttpClient client = new HttpClient();
+    HttpClient client = new HttpClient(context: clientContext);
 
     client.findProxy = (Uri uri) {
       return HttpClient.findProxyFromEnvironment(
           uri,
           environment: {"http_proxy": "localhost:${proxyServer.port}",
                         "https_proxy": "localhost:${proxyServer.port}"});
     };
 
     const int loopCount = 5;
     for (int i = 0; i < loopCount; i++) {
@@ skipping 33 matching lines @@
 
 
 int testProxyAuthenticateCount = 0;
 Future testProxyAuthenticate(bool useDigestAuthentication) {
   testProxyAuthenticateCount = 0;
   var completer = new Completer();
 
   setupProxyServer().then((proxyServer) {
   setupServer(1).then((server) {
   setupServer(1, secure: true).then((secureServer) {
-    HttpClient client = new HttpClient();
+    HttpClient client = new HttpClient(context: clientContext);
 
     Completer step1 = new Completer();
     Completer step2 = new Completer();
 
     if (useDigestAuthentication) {
       proxyServer.useDigestAuthentication("dart", "password");
     } else {
       proxyServer.useBasicAuthentication("dart", "password");
     }
 
@@ skipping 128 matching lines @@
   });
   });
   });
 
   return completer.future;
 }
 
 int testRealProxyDoneCount = 0;
 void testRealProxy() {
   setupServer(1).then((server) {
-    HttpClient client = new HttpClient();
+    HttpClient client = new HttpClient(context: clientContext);
      client.addProxyCredentials(
          "localhost",
          8080,
          "test",
          new HttpClientBasicCredentials("dart", "password"));
 
     List<String> proxy =
         ["PROXY localhost:8080",
          "PROXY localhost:8080; PROXY hede.hule.hest:8080",
          "PROXY hede.hule.hest:8080; PROXY localhost:8080",
@@ skipping 22 matching lines @@
             }
           });
         });
     }
   });
 }
 
 int testRealProxyAuthDoneCount = 0;
 void testRealProxyAuth() {
   setupServer(1).then((server) {
-    HttpClient client = new HttpClient();
+    HttpClient client = new HttpClient(context: clientContext);
 
     List<String> proxy =
         ["PROXY dart:password@localhost:8080",
          "PROXY dart:password@localhost:8080; PROXY hede.hule.hest:8080",
          "PROXY hede.hule.hest:8080; PROXY dart:password@localhost:8080",
          "PROXY dart:password@localhost:8080; DIRECT"];
 
     client.findProxy = (Uri uri) {
       // Pick the proxy configuration based on the request path.
       int index = int.parse(uri.path.substring(1));
@@ skipping 27 matching lines @@
   // The two invocations use the same global variable for state -
   // run one after the other.
   testProxyAuthenticate(false)
       .then((_) => testProxyAuthenticate(true));
 
   // This test is not normally run. It can be used for locally testing
   // with a real proxy server (e.g. Apache).
   // testRealProxy();
   // testRealProxyAuth();
 }