gn/linux: warnings as errors, turn on Wextra

ui/keyboard/keyboard_util.cc

Index: ui/keyboard/keyboard_util.cc
diff --git a/ui/keyboard/keyboard_util.cc b/ui/keyboard/keyboard_util.cc
index 438b99c22f683e799d9cf7a8a3652514d6999bab..188aa73fb398f147e197ecfcc1c2ab46bff3efa1 100644
--- a/ui/keyboard/keyboard_util.cc
+++ b/ui/keyboard/keyboard_util.cc
@@ -285,12 +285,12 @@ bool SendKeyEvent(const std::string type,
   return true;
 }
 
-const void MarkKeyboardLoadStarted() {
+void MarkKeyboardLoadStarted() {
   if (!g_keyboard_load_time_start.Get().ToInternalValue())
     g_keyboard_load_time_start.Get() = base::Time::Now();
 }
 
-const void MarkKeyboardLoadFinished() {
+void MarkKeyboardLoadFinished() {
   // Possible to get a load finished without a start if navigating directly to
   // chrome://keyboard.
   if (!g_keyboard_load_time_start.Get().ToInternalValue())