Disable Panels on OSes other than ChromeOS, in preparation to removing the code.

chrome/browser/ui/panels/panel_manager.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/ui/panels/panel_manager.h"
 
 #include <memory>
 
 #include "base/bind.h"
 #include "base/command_line.h"
@@ skipping 89 matching lines @@
 }
 
 // static
 void PanelManager::SetDisplaySettingsProviderForTesting(
     DisplaySettingsProvider* provider) {
   display_settings_provider_for_testing = provider;
 }
 
 // static
 bool PanelManager::ShouldUsePanels(const std::string& extension_id) {
-  // If --disable-panels is on, never use panels.
-  if (base::CommandLine::ForCurrentProcess()->HasSwitch(
-          switches::kDisablePanels))

[Evan Stade, 2016/06/21 21:18:23]

Did you consider leaving the flags alone and just inverting this check, i.e.
!HasSwitch(enable)

[Dmitry Titov, 2016/06/22 00:29:28]

Done, keep switches working for now, changing default. Since it'll remain
enabled for ChromeOS, the check is a bit different...

-    return false;
-
   // If --enable-panels is on, always use panels.
   if (base::CommandLine::ForCurrentProcess()->HasSwitch(
           switches::kEnablePanels))
     return true;
 
+// Panels are an Eraser target. See http://crbug.com/571511 for details.
+// TODO(dimich): remove the rest of Panels code once erasure is stable.
+#if !defined(OS_CHROMEOS)
+  return false;
+#endif  // !OS_CHROMEOS
+
 #if defined(USE_X11) && !defined(OS_CHROMEOS)
   // On Linux, panels are only supported on tested window managers.
   ui::WindowManagerName wm_type = ui::GuessWindowManager();
   if (wm_type != ui::WM_COMPIZ &&
       wm_type != ui::WM_ICE_WM &&
       wm_type != ui::WM_KWIN &&
       wm_type != ui::WM_METACITY &&
       wm_type != ui::WM_MUFFIN &&
       wm_type != ui::WM_MUTTER &&
       wm_type != ui::WM_XFWM4) {
@@ skipping 439 matching lines @@
 void PanelManager::SetMouseWatcher(PanelMouseWatcher* watcher) {
   panel_mouse_watcher_.reset(watcher);
 }
 
 void PanelManager::OnPanelAnimationEnded(Panel* panel) {
   content::NotificationService::current()->Notify(
       chrome::NOTIFICATION_PANEL_BOUNDS_ANIMATIONS_FINISHED,
       content::Source<Panel>(panel),
       content::NotificationService::NoDetails());
 }