[ios] Do not lock schemes registry in WebTest.

ios/web/test/web_test.mm

 // Copyright 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #import "ios/web/test/web_test.h"
 
 #include <utility>
 
 #include "base/base64.h"
 #include "base/memory/ptr_util.h"
@@ skipping 23 matching lines @@
 }
 @end
 
 namespace web {
 
 #pragma mark -
 
 WebTest::WebTest() : web_client_(base::WrapUnique(new TestWebClient)) {
   static dispatch_once_t onceToken;
   dispatch_once(&onceToken, ^{
-    RegisterWebSchemes(true);
+    RegisterWebSchemes(false);
   });
 }
 
 WebTest::~WebTest() {}
 
 void WebTest::SetUp() {
   PlatformTest::SetUp();
   BrowserState::GetActiveStateManager(&browser_state_)->SetActive(true);
 }
 
@@ skipping 163 matching lines @@
   }
   return false;
 }
 
 NSString* WebTestWithWebController::CreateLoadCheck() {
   return [NSString stringWithFormat:@"<p style=\"display: none;\">%d</p>",
                                     s_html_load_count++];
 }
 
 }  // namespace web