Enable SiteIsolationExtensions trial for developers.

chrome/browser/extensions/extension_apitest.h

 // Copyright (c) 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.
 
 #ifndef CHROME_BROWSER_EXTENSIONS_EXTENSION_APITEST_H_
 #define CHROME_BROWSER_EXTENSIONS_EXTENSION_APITEST_H_
 
 #include <deque>
 #include <string>
 
@@ skipping 47 matching lines @@
     // Allow manifest versions older that Extension::kModernManifestVersion.
     // Used to test old manifest features.
     kFlagAllowOldManifestVersions = 1 << 6,
   };
 
   ExtensionApiTest();
   ~ExtensionApiTest() override;
 
  protected:
   // InProcessBrowserTest:
-  void SetUpInProcessBrowserTestFixture() override;
+  void SetUpOnMainThread() override;
   void TearDownInProcessBrowserTestFixture() override;
 
   // Load |extension_name| and wait for pass / fail notification.
   // |extension_name| is a directory in "test/data/extensions/api_test".
   bool RunExtensionTest(const std::string& extension_name);
 
   // Similar to RunExtensionTest, except sets an additional string argument
   // |customArg| to the test config object.
   bool RunExtensionTestWithArg(const std::string& extension_name,
                                const char* custom_arg);
@@ skipping 122 matching lines @@
   std::unique_ptr<base::DictionaryValue> test_config_;
 
   // Hold the test WebSocket server.
   std::unique_ptr<net::SpawnedTestServer> websocket_server_;
 
   // Hold the test FTP server.
   std::unique_ptr<net::SpawnedTestServer> ftp_server_;
 };
 
 #endif  // CHROME_BROWSER_EXTENSIONS_EXTENSION_APITEST_H_