The key event should be stopped propagation when it's been processed as an accelerator.

ui/views/widget/desktop_aura/desktop_native_widget_aura.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/views/widget/desktop_aura/desktop_native_widget_aura.h"
 
 #include "base/bind.h"
 #include "base/macros.h"
 #include "base/trace_event/trace_event.h"
 #include "build/build_config.h"
@@ skipping 202 matching lines @@
  public:
   explicit FocusManagerEventHandler(
       DesktopNativeWidgetAura* desktop_native_widget_aura)
       : desktop_native_widget_aura_(desktop_native_widget_aura) {}
 
   // Implementation of ui::EventHandler:
   void OnKeyEvent(ui::KeyEvent* event) override {
     Widget* widget = desktop_native_widget_aura_->GetWidget();
     if (widget && widget->GetFocusManager()->GetFocusedView() &&
         !widget->GetFocusManager()->OnKeyEvent(*event)) {
-      event->SetHandled();
+      event->StopPropagation();
     }
   }
 
  private:
   DesktopNativeWidgetAura* desktop_native_widget_aura_;
 
   DISALLOW_COPY_AND_ASSIGN(FocusManagerEventHandler);
 };
 
 class RootWindowDestructionObserver : public aura::WindowObserver {
@@ skipping 794 matching lines @@
   // Renderer may send a key event back to us if the key event wasn't handled,
   // and the window may be invisible by that time.
   if (!content_window_->IsVisible())
     return;
 
   native_widget_delegate_->OnKeyEvent(event);
   if (event->handled())
     return;
 
   if (GetWidget()->HasFocusManager() &&
-      !GetWidget()->GetFocusManager()->OnKeyEvent(*event))
-    event->SetHandled();
+      !GetWidget()->GetFocusManager()->OnKeyEvent(*event)) {
+    event->StopPropagation();
+  }
 }
 
 void DesktopNativeWidgetAura::OnMouseEvent(ui::MouseEvent* event) {
   DCHECK(content_window_->IsVisible());
   if (tooltip_manager_.get())
     tooltip_manager_->UpdateTooltip();
   TooltipManagerAura::UpdateTooltipManagerForCapture(GetWidget());
   native_widget_delegate_->OnMouseEvent(event);
   // WARNING: we may have been deleted.
 }
@@ skipping 136 matching lines @@
   if (cursor_reference_count_ == 0) {
     // We are the last DesktopNativeWidgetAura instance, and we are responsible
     // for cleaning up |cursor_manager_|.
     delete cursor_manager_;
     native_cursor_manager_ = NULL;
     cursor_manager_ = NULL;
   }
 }
 
 }  // namespace views