events: Update mouse-event handlers to not return EventResult.

chrome/browser/ui/views/immersive_mode_controller.cc

Index: chrome/browser/ui/views/immersive_mode_controller.cc
diff --git a/chrome/browser/ui/views/immersive_mode_controller.cc b/chrome/browser/ui/views/immersive_mode_controller.cc
index be46397795e85edaceba8605f91e986d42700ce3..3f59bf34662e4b25b1a5a23c980a1e4c998f5ff9 100644
--- a/chrome/browser/ui/views/immersive_mode_controller.cc
+++ b/chrome/browser/ui/views/immersive_mode_controller.cc
@@ -296,9 +296,9 @@ void ImmersiveModeController::MaybeStackViewAtTop() {
 }
 
 // ui::EventHandler overrides:
-ui::EventResult ImmersiveModeController::OnMouseEvent(ui::MouseEvent* event) {
+void ImmersiveModeController::OnMouseEvent(ui::MouseEvent* event) {
   if (event->type() != ui::ET_MOUSE_MOVED)
-    return ui::ER_UNHANDLED;
+    return;
   if (event->location().y() == 0) {
     // Use a timer to detect if the cursor stays at the top past a delay.
     if (!top_timer_.IsRunning()) {
@@ -311,7 +311,6 @@ ui::EventResult ImmersiveModeController::OnMouseEvent(ui::MouseEvent* event) {
     top_timer_.Stop();
   }
   // Pass along event for further handling.
-  return ui::ER_UNHANDLED;
 }
 
 // ui::ImplicitAnimationObserver overrides: