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

chrome/browser/ui/panels/panel_manager.cc

Index: chrome/browser/ui/panels/panel_manager.cc
diff --git a/chrome/browser/ui/panels/panel_manager.cc b/chrome/browser/ui/panels/panel_manager.cc
index 7d2c9cec5a78d650b69545e879eab81a9327f98c..819f76a913fdf3fc33e03fedca8d1999e0a9f6e9 100644
--- a/chrome/browser/ui/panels/panel_manager.cc
+++ b/chrome/browser/ui/panels/panel_manager.cc
@@ -107,16 +107,17 @@ void PanelManager::SetDisplaySettingsProviderForTesting(
 
 // 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();