Handle F6 and F7 (brightness keys) in ash [part 3 of 3].

ui/base/keycodes/keyboard_code_conversion_x.cc

Index: ui/base/keycodes/keyboard_code_conversion_x.cc
diff --git a/ui/base/keycodes/keyboard_code_conversion_x.cc b/ui/base/keycodes/keyboard_code_conversion_x.cc
index 23511f6e7f6c839feb9f7bcbcd4c7b7ec27cb476..a1bb6ecbac3aea52204c2a7c8d25d09dcc739e31 100644
--- a/ui/base/keycodes/keyboard_code_conversion_x.cc
+++ b/ui/base/keycodes/keyboard_code_conversion_x.cc
@@ -355,6 +355,10 @@ KeyboardCode KeyboardCodeFromXKeysym(unsigned int keysym) {
       return VKEY_VOLUME_DOWN;
     case XF86XK_AudioRaiseVolume:
       return VKEY_VOLUME_UP;
+    case XF86XK_MonBrightnessDown:
+      return VKEY_BRIGHTNESS_DOWN;
+    case XF86XK_MonBrightnessUp:
+      return VKEY_BRIGHTNESS_UP;
 
     // TODO(sad): some keycodes are still missing.
   }
@@ -673,6 +677,10 @@ int XKeysymForWindowsKeyCode(KeyboardCode keycode, bool shift) {
       return XF86XK_AudioLowerVolume;
     case VKEY_VOLUME_UP:
       return XF86XK_AudioRaiseVolume;
+    case VKEY_BRIGHTNESS_DOWN:
+      return XF86XK_MonBrightnessDown;
+    case VKEY_BRIGHTNESS_UP:
+      return XF86XK_MonBrightnessUp;
 
     default:
       LOG(WARNING) << "Unknown keycode:" << keycode;