Fix panel showing logic when Chrome enters the fullscreen mode

chrome/browser/ui/cocoa/panels/panel_cocoa.mm

Index: chrome/browser/ui/cocoa/panels/panel_cocoa.mm
diff --git a/chrome/browser/ui/cocoa/panels/panel_cocoa.mm b/chrome/browser/ui/cocoa/panels/panel_cocoa.mm
index 722d88ed24bbe7f2db2ddfa78a63d2fc9319d6c8..3c0e79a50dc2344870bb56abfa8026d9f9f1c65e 100644
--- a/chrome/browser/ui/cocoa/panels/panel_cocoa.mm
+++ b/chrome/browser/ui/cocoa/panels/panel_cocoa.mm
@@ -210,8 +210,22 @@ void PanelCocoa::HandlePanelKeyboardEvent(
   [event_window redispatchKeyEvent:event.os_event];
 }
 
-void PanelCocoa::FullScreenModeChanged(
-    bool is_full_screen) {
+void PanelCocoa::FullScreenModeChanged(bool is_full_screen) {
+  if (!is_shown_) {
+    // If the panel window is not shown due to that a Chrome tab window is in
+    // fullscreen mode when the panel is being created, we need to show the
+    // panel window now. In addition, its titlebar needs to be updated since it
+    // is not done at the panel creation time.
+    if (!is_full_screen) {
+      ShowPanelInactive();
+      UpdatePanelTitleBar();
+    }
+
+    // No need to proceed when the panel window was not shown previously.
+    // We either show the panel window or do not show it depending on current
+    // full screen state.
+    return;
+  }
   [controller_ fullScreenModeChanged:is_full_screen];
 }