Create system tray item for accessing chrome://slow

ash/system/tray/system_tray_delegate.h

Index: ash/system/tray/system_tray_delegate.h
diff --git a/ash/system/tray/system_tray_delegate.h b/ash/system/tray/system_tray_delegate.h
index d6f3c3dbe493d3465202b8a49677a0f90ebb19f2..0dcc07d9c968684cda49b9022cf01f6b678d4a65 100644
--- a/ash/system/tray/system_tray_delegate.h
+++ b/ash/system/tray/system_tray_delegate.h
@@ -169,6 +169,9 @@ class SystemTrayDelegate {
   // Shows settings related to multiple displays.
   virtual void ShowDisplaySettings() = 0;
 
+  // Shows the page that lets you disable performance tracing.
+  virtual void ShowChromeSlow() = 0;
+
   // Returns true if the notification for the display configuration change
   // should appear.
   virtual bool ShouldShowDisplayNotification() = 0;