chromeos: Add external brightness control to chrome://flags.

chrome/app/generated_resources.grd

Index: chrome/app/generated_resources.grd
diff --git a/chrome/app/generated_resources.grd b/chrome/app/generated_resources.grd
index 9b967cb4d15b3fb7a88945c1bc400c836ff5d290..90be681fb28d0d2bb532e0bdc45ad2b19c67f302 100644
--- a/chrome/app/generated_resources.grd
+++ b/chrome/app/generated_resources.grd
@@ -6294,6 +6294,12 @@ Keep your key file in a safe place. You will need it to create new versions of y
       <message name="IDS_FLAGS_ASH_ENABLE_TOUCH_VIEW_TESTING_DESCRIPTION" desc="Description for the flag to enable the TouchView testing mode.">
         Enable Ctrl+Alt+Shift+D to toggle the TouchView maximizing mode.
       </message>
+      <message name="IDS_FLAGS_ASH_ENABLE_BRIGHTNESS_CONTROL_NAME" desc="Title for the flag which can be used to enable brightness control of external displays.">
+        Enable brightness control of external displays
+      </message>
+      <message name="IDS_FLAGS_ASH_ENABLE_BRIGHTNESS_CONTROL_DESCRIPTION" desc="Description for the flag to enable brightness control of external displays.">
+        Make the brightness keys adjust external displays' brightness levels on devices that don't have internal displays.
+      </message>
       <message name="IDS_FLAGS_ENABLE_FULL_MULTI_PROFILE_MODE" desc="Title for the full multi profile mode flag.">
         Enable side-by-side multi profile mode
       </message>