Fix flaky linux panel tests related to active state checks

chrome/browser/ui/panels/base_panel_browser_test.cc

Index: chrome/browser/ui/panels/base_panel_browser_test.cc
diff --git a/chrome/browser/ui/panels/base_panel_browser_test.cc b/chrome/browser/ui/panels/base_panel_browser_test.cc
index 764a9e4ce8e6abd7d8238d0b6c792806bc6d5371..1edc5bcec9575962801c6da4d83916cfd8ad5a52 100644
--- a/chrome/browser/ui/panels/base_panel_browser_test.cc
+++ b/chrome/browser/ui/panels/base_panel_browser_test.cc
@@ -328,14 +328,16 @@ Panel* BasePanelBrowserTest::CreatePanelWithParams(
   }
 
   if (params.wait_for_fully_created) {
-    MessageLoopForUI::current()->RunAllPending();
-
 #if defined(OS_LINUX)
     // On bots, we might have a simple window manager which always activates new
     // windows, and can't always deactivate them. Re-activate the main tabbed
     // browser to "deactivate" the newly created panel.
     if (params.expected_active_state == SHOW_AS_INACTIVE &&
         ui::GuessWindowManager() == ui::WM_ICE_WM) {
+      // Wait for new panel to become active before deactivating to ensure
+      // the activated notification is consumed before we wait for the panel
+      // to become inactive.
+      WaitForPanelActiveState(panel, SHOW_AS_ACTIVE);
       browser()->window()->Activate();
     }
 #endif