Fix "unreachable code" warnings (MSVC warning 4702) in ui/.

ui/views/widget/widget.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/widget.h"
 
 #include "base/debug/trace_event.h"
 #include "base/logging.h"
 #include "base/message_loop/message_loop.h"
 #include "base/strings/utf_string_conversions.h"
@@ skipping 1146 matching lines @@
       if (root_view && root_view->OnMousePressed(*event) &&
           widget_deletion_observer.IsWidgetAlive() && IsVisible() &&
           internal::NativeWidgetPrivate::IsMouseButtonDown()) {
         is_mouse_button_pressed_ = true;
         if (!native_widget_->HasCapture())
           native_widget_->SetCapture();
         event->SetHandled();
       }
       return;
     }
+
     case ui::ET_MOUSE_RELEASED:
       last_mouse_event_was_move_ = false;
       is_mouse_button_pressed_ = false;
       // Release capture first, to avoid confusion if OnMouseReleased blocks.
       if (auto_release_capture_ && native_widget_->HasCapture())
         native_widget_->ReleaseCapture();
       if (root_view)
         root_view->OnMouseReleased(*event);
       if ((event->flags() & ui::EF_IS_NON_CLIENT) == 0)
         event->SetHandled();
       return;
+
     case ui::ET_MOUSE_MOVED:
     case ui::ET_MOUSE_DRAGGED:
       if (native_widget_->HasCapture() && is_mouse_button_pressed_) {
         last_mouse_event_was_move_ = false;
         if (root_view)
           root_view->OnMouseDragged(*event);
       } else if (!last_mouse_event_was_move_ ||
                  last_mouse_event_position_ != event->location()) {
         last_mouse_event_position_ = event->location();
         last_mouse_event_was_move_ = true;
         if (root_view)
           root_view->OnMouseMoved(*event);
       }
       return;
+
     case ui::ET_MOUSE_EXITED:
       last_mouse_event_was_move_ = false;
       if (root_view)
         root_view->OnMouseExited(*event);
       return;
+
     case ui::ET_MOUSEWHEEL:
       if (root_view && root_view->OnMouseWheel(
           static_cast<const ui::MouseWheelEvent&>(*event)))
         event->SetHandled();
       return;
+
     default:
       return;
   }
-  event->SetHandled();
 }
 
 void Widget::OnMouseCaptureLost() {
   if (is_mouse_button_pressed_ || is_touch_down_) {
     View* root_view = GetRootView();
     if (root_view)
       root_view->OnMouseCaptureLost();
   }
   is_touch_down_ = false;
   is_mouse_button_pressed_ = false;
@@ skipping 228 matching lines @@
 
 ////////////////////////////////////////////////////////////////////////////////
 // internal::NativeWidgetPrivate, NativeWidget implementation:
 
 internal::NativeWidgetPrivate* NativeWidgetPrivate::AsNativeWidgetPrivate() {
   return this;
 }
 
 }  // namespace internal
 }  // namespace views