Enable the EnablePhysicalWeb flag by default on Chrome for iOS

ios/chrome/browser/experimental_flags.mm

 // Copyright 2015 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.
 
 // This file can be empty. Its purpose is to contain the relatively short lived
 // definitions required for experimental flags.
 
 #include "ios/chrome/browser/experimental_flags.h"
 
 #include <dispatch/dispatch.h>
@@ skipping 196 matching lines @@
 }
 
 bool IsPhysicalWebEnabled() {
   base::CommandLine* command_line = base::CommandLine::ForCurrentProcess();
   if (command_line->HasSwitch(switches::kEnableIOSPhysicalWeb)) {
     return true;
   } else if (command_line->HasSwitch(switches::kDisableIOSPhysicalWeb)) {
     return false;
   }
 
-  // Check if the finch experiment is turned on
+  // Check if the Finch experiment is turned on.
   std::string group_name =
       base::FieldTrialList::FindFullName("PhysicalWebEnabled");
-  return base::StartsWith(group_name, "Enabled",
-                          base::CompareCase::INSENSITIVE_ASCII);
+  // The feature is enabled by default.
+  return !base::StartsWith(group_name, "Disabled",
+                           base::CompareCase::INSENSITIVE_ASCII);
 }
 
 bool IsReaderModeEnabled() {
   return base::CommandLine::ForCurrentProcess()->HasSwitch(
       switches::kEnableReaderModeToolbarIcon);
 }
 
 bool IsReadingListEnabled() {
   return reading_list::switches::IsReadingListEnabled();
 }
@@ skipping 37 matching lines @@
     return true;
 
   if (command_line->HasSwitch(switches::kDisableSuggestionsUI))
     return false;
 
   // By default, disable it.
   return false;
 }
 
 }  // namespace experimental_flags