Fix flaky linux panel tests related to active state checks

chrome/browser/ui/panels/old_panel_drag_browsertest.cc

Index: chrome/browser/ui/panels/old_panel_drag_browsertest.cc
diff --git a/chrome/browser/ui/panels/old_panel_drag_browsertest.cc b/chrome/browser/ui/panels/old_panel_drag_browsertest.cc
index 28b655480c74c7325ea79461759bb4bf3e0305a1..023877d0d526a03b613c929e79970b775342a0e5 100644
--- a/chrome/browser/ui/panels/old_panel_drag_browsertest.cc
+++ b/chrome/browser/ui/panels/old_panel_drag_browsertest.cc
@@ -12,9 +12,6 @@
 #include "chrome/browser/ui/panels/panel_manager.h"
 #include "chrome/browser/ui/panels/test_panel_mouse_watcher.h"
 
-// Panel tests are flaking on linux CQ. http://crbug.com/135377
-#if !defined(OS_LINUX)
-
 class OldPanelDragBrowserTest : public OldBasePanelBrowserTest {
  public:
   OldPanelDragBrowserTest() : OldBasePanelBrowserTest() {
@@ -1350,5 +1347,3 @@ IN_PROC_BROWSER_TEST_F(OldPanelDragBrowserTest, DragDetachedPanelToTop) {
 
   panel_manager->CloseAll();
 }
-
-#endif  // !OS_LINUX