Reverse the embedded-shared-worker flag to turn the feature on by default.

chrome/browser/about_flags.cc

 // 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.
 
 #include "chrome/browser/about_flags.h"
 
 #include <algorithm>
 #include <iterator>
 #include <map>
 #include <set>
@@ skipping 1763 matching lines @@
 #if defined(GOOGLE_CHROME_BUILD)
   {
     "enable-easy-unlock",
     IDS_FLAGS_ENABLE_EASY_UNLOCK_NAME,
     IDS_FLAGS_ENABLE_EASY_UNLOCK_DESCRIPTION,
     kOsCrOS,
     SINGLE_VALUE_TYPE(switches::kEnableEasyUnlock)
   },
 #endif
   {
-    "enable-embedded-shared-worker",
-    IDS_FLAGS_ENABLE_EMBEDDED_SHARED_WORKER_NAME,
-    IDS_FLAGS_ENABLE_EMBEDDED_SHARED_WORKER_DESCRIPTION,
+    "disable-embedded-shared-worker",
+    IDS_FLAGS_DISABLE_EMBEDDED_SHARED_WORKER_NAME,
+    IDS_FLAGS_DISABLE_EMBEDDED_SHARED_WORKER_DESCRIPTION,
     kOsDesktop,
-    SINGLE_VALUE_TYPE(switches::kEnableEmbeddedSharedWorker)
+    SINGLE_VALUE_TYPE(switches::kDisableEmbeddedSharedWorker)
   },
 #if defined(OS_CHROMEOS)
   {
     "enable-filemanager-mtp",
     IDS_FLAGS_ENABLE_FILE_MANAGER_MTP_NAME,
     IDS_FLAGS_ENABLE_FILE_MANAGER_MTP_DESCRIPTION,
     kOsCrOS,
     SINGLE_VALUE_TYPE(chromeos::switches::kEnableFileManagerMTP)
   },
 #endif
@@ skipping 514 matching lines @@
 }
 
 const Experiment* GetExperiments(size_t* count) {
   *count = num_experiments;
   return experiments;
 }
 
 }  // namespace testing
 
 }  // namespace about_flags