Allow 'Alt+Shift+K' to show IME menu at login or lock screen.

Add accelerator SHOW_IME_MENU_BUBBLE into table kActionsAllowedAtLoginOrLockScreen to allow using 'Alt+Shift+K' to open opt-in IME menu in login or lock screen.

BUG=668394,642423
TEST=Verified on local build.

Review-Url: https://codereview.chromium.org/2566583004
Cr-Commit-Position: refs/heads/master@{#437978}

ash/common/accelerators/accelerator_table.cc

@@ -341,6 +341,7 @@ const AcceleratorAction kActionsAllowedAtLoginOrLockScreen[] = {
     DISABLE_CAPS_LOCK,
     KEYBOARD_BRIGHTNESS_DOWN,
     KEYBOARD_BRIGHTNESS_UP,
+    SHOW_IME_MENU_BUBBLE,
     TOGGLE_CAPS_LOCK,
     TOGGLE_HIGH_CONTRAST,
     TOGGLE_SPOKEN_FEEDBACK,