Introduce "Preferred" accelerators

ash/accelerators/accelerator_table.cc

Index: ash/accelerators/accelerator_table.cc
diff --git a/ash/accelerators/accelerator_table.cc b/ash/accelerators/accelerator_table.cc
index fd9ab7f1bea4d4d01fb3a576db85eb65f9a62702..a4a0c52b83eaad2cd9605c7e4efacde8b9370895 100644
--- a/ash/accelerators/accelerator_table.cc
+++ b/ash/accelerators/accelerator_table.cc
@@ -231,13 +231,20 @@ const AcceleratorData kDebugAcceleratorData[] = {
 
 const size_t kDebugAcceleratorDataLength = arraysize(kDebugAcceleratorData);
 
-const AcceleratorAction kReservedActions[] = {
+const AcceleratorAction kPreferredActions[] = {
   // Window cycling accelerators.
   CYCLE_BACKWARD_MRU,  // Shift+Alt+Tab
   CYCLE_FORWARD_MRU,  // Alt+Tab
+};
+
+const size_t kPreferredActionsLength = arraysize(kPreferredActions);
+
+const AcceleratorAction kReservedActions[] = {
 #if defined(OS_CHROMEOS)
   POWER_PRESSED,
   POWER_RELEASED,
+#else
+  DUMMY_FOR_RESERVED,
 #endif
 };