app_list: Disable Drive app integration for M39.

ui/app_list/app_list_switches.cc

 // Copyright 2013 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 "ui/app_list/app_list_switches.h"
 
 #include "base/command_line.h"
 
 namespace app_list {
 namespace switches {
@@ skipping 60 matching lines @@
       kEnableExperimentalAppList);
 }
 
 bool IsCenteredAppListEnabled() {
   return CommandLine::ForCurrentProcess()->HasSwitch(kEnableCenteredAppList) ||
          IsExperimentalAppListEnabled();
 }
 
 bool IsDriveAppsInAppListEnabled() {
 #if defined(OS_CHROMEOS)
-  return !CommandLine::ForCurrentProcess()->HasSwitch(
-      kDisableDriveAppsInAppList);
+  // Disable Drive app integration due to http://crbug.com/420034
+  // TODO(xiyuan): Revisit this after the bug is fixed.
+  return false;
 #else
   return false;
 #endif
 }
 
 }  // namespace switches
 }  // namespace app_list