Control zero suggest with a pref, not a switch.

chrome/common/chrome_switches.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/common/chrome_switches.h"
 
 #include "base/base_switches.h"
 #include "base/command_line.h"
 
 namespace switches {
@@ skipping 656 matching lines @@
 // experimental feature is auto spell correct, which corrects words which are
 // misspelled by typing the word with two consecutive letters swapped. The
 // features that will be added next are:
 //
 // 1 - Allow multiple spellcheckers to work simultaneously.
 // 2 - Allow automatic detection of spell check language.
 // TODO(sidchat): Implement the above features to work under this flag.
 const char kExperimentalSpellcheckerFeatures[] =
     "experimental-spellchecker-features";
 
-// If nonempty, fetch experimental zero-suggest suggestions by appending to
-// this prefix of a URL.
-const char kExperimentalZeroSuggestURLPrefix[] =
-    "experimental-zero-suggest-url-prefix";
-
 // Explicitly allows additional ports using a comma-separated list of port
 // numbers.
 const char kExplicitlyAllowedPorts[]        = "explicitly-allowed-ports";
 
 // The time in seconds that an extension event page can be idle before it
 // is shut down.
 const char kEventPageIdleTime[]             = "event-page-idle-time";
 
 // The time in seconds that an extension event page has between being notified
 // of its impending unload and that unload happening.
@@ skipping 885 matching lines @@
 
 // -----------------------------------------------------------------------------
 // DO NOT ADD YOUR CRAP TO THE BOTTOM OF THIS FILE.
 //
 // You were going to just dump your switches here, weren't you? Instead, please
 // put them in alphabetical order above, or in order inside the appropriate
 // ifdef at the bottom. The order should match the header.
 // -----------------------------------------------------------------------------
 
 }  // namespace switches