[iOS] Enable support for finch experiment for Open from Clipboard.

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 <string>
@@ skipping 13 matching lines @@
 
 namespace experimental_flags {
 
 bool IsAlertOnBackgroundUploadEnabled() {
   return [[NSUserDefaults standardUserDefaults]
       boolForKey:kEnableAlertOnBackgroundUpload];
 }
 
 bool IsOpenFromClipboardEnabled() {
   base::CommandLine* command_line = base::CommandLine::ForCurrentProcess();
-  return command_line->HasSwitch(switches::kEnableIOSOpenFromClipboard);
+  if (command_line->HasSwitch(switches::kEnableIOSOpenFromClipboard))
+    return true;
+  return base::FieldTrialList::FindFullName("IOSOpenFromClipboard") ==
+         "Enabled";
 }
 
 bool IsWKWebViewEnabled() {
   // If WKWebView isn't supported, don't activate the experiment at all. This
   // avoids someone being slotted into the WKWebView bucket (and thus reporting
   // as WKWebView), but actually running UIWebView.
   if (!web::IsWKWebViewSupported())
     return false;
 
   std::string group_name =
@@ skipping 26 matching lines @@
   }
 
   // Parse the value.
   size_t wedge_size_in_mb = 0;
   if (base::StringToSizeT(wedge_size_string, &wedge_size_in_mb))
     return wedge_size_in_mb;
   return 0;
 }
 
 }  // namespace experimental_flags