Hot track the child button when the mouse hovering on the host item

MenuController::HandleMouseLocation() called in
MenuController::OnMouseMoved() calls MenuController::SetSelection()
which may reset the hot-tracked view. Meanwhile, in OnMouseMoved(),
the hot-tracked view updates before HandleMouseLocation(). As a result,
the hot-tracked view may fail to update after the mouse move event.

This bug should have existed for long time. But it is not noticeable
on real devices: when a user moves the mouse, it usually creates more
than one mouse move events. Then the second mouse move event updates
the hot-tracked view.

This CL updates the hot-tracked view after HandleMouseLocation().

Bug: 1135000
Change-Id: Iae810563e897d75912bcc140ed56022d72e3170c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2448650Reviewed-by: Scott Violet <sky@chromium.org>
Commit-Queue: Andrew Xu <andrewxu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#814039}

ui/views/controls/menu/menu_controller.cc

@@ -837,6 +837,7 @@ void MenuController::OnMouseMoved(SubmenuView* source,
 
   menu_open_mouse_loc_.reset();
   MenuHostRootView* root_view = GetRootView(source, event.location());
+  Button* new_hot_tracked_button = nullptr;
   if (root_view) {
     root_view->ProcessMouseMoved(event);
 
@@ -846,12 +847,15 @@ void MenuController::OnMouseMoved(SubmenuView* source,
     ui::MouseEvent event_for_root(event);
     ConvertLocatedEventForRootView(source, root_view, &event_for_root);
     View* view = root_view->GetEventHandlerForPoint(event_for_root.location());
-    Button* button = Button::AsButton(view);
-    if (button)
-      SetHotTrackedButton(button);
+    new_hot_tracked_button = Button::AsButton(view);
   }
 
   HandleMouseLocation(source, event.location());
+
+  // Updating the hot tracked button should be after `HandleMouseLocation()`
+  // which may reset the current hot tracked button.
+  if (new_hot_tracked_button)
+    SetHotTrackedButton(new_hot_tracked_button);
 }
 
 void MenuController::OnMouseEntered(SubmenuView* source,

ui/views/controls/menu/menu_controller_unittest.cc

@@ -1370,6 +1370,31 @@ TEST_F(MenuControllerTest, DeleteChildButtonView) {
   EXPECT_FALSE(button3->IsHotTracked());
 }
 
+// Verifies that the child button of the menu item which is under mouse hovering
+// is hot tracked (https://crbug.com/1135000).
+TEST_F(MenuControllerTest, ChildButtonHotTrackedAfterMouseMove) {
+  // Add a menu item which owns a button as child.
+  menu_item()->SetBounds(0, 0, 200, 300);
+  MenuItemView* button_host_view =
+      menu_item()->AppendMenuItem(/*command_id=*/5);
+  auto* button = button_host_view->AddChildView(
+      std::make_unique<LabelButton>(nullptr, base::ASCIIToUTF16("Label")));
+  button->SetFocusBehavior(View::FocusBehavior::ALWAYS);
+  menu_item()->GetSubmenu()->ShowAt(owner(), menu_item()->bounds(), false);
+  EXPECT_FALSE(button->IsHotTracked());
+
+  SubmenuView* sub_menu = menu_item()->GetSubmenu();
+  gfx::Point location(button->GetBoundsInScreen().CenterPoint());
+  View::ConvertPointFromScreen(sub_menu->GetScrollViewContainer(), &location);
+  ui::MouseEvent event(ui::ET_MOUSE_MOVED, location, location,
+                       ui::EventTimeForNow(), 0, 0);
+  ProcessMouseMoved(sub_menu, event);
+
+  // After the mouse moves to `button`, `button` should be hot tracked.
+  EXPECT_EQ(button, GetHotButton());
+  EXPECT_TRUE(button->IsHotTracked());
+}
+
 // Creates a menu with Button child views, simulates running a nested
 // menu and tests that existing the nested run restores hot-tracked child view.
 TEST_F(MenuControllerTest, ChildButtonHotTrackedWhenNested) {