Fix flaky linux panel tests related to active state checks

chrome/browser/ui/panels/test_panel_active_state_observer.h

+// 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.
+
+#ifndef CHROME_BROWSER_UI_PANELS_TEST_PANEL_ACTIVE_STATE_OBSERVER_H_
+#define CHROME_BROWSER_UI_PANELS_TEST_PANEL_ACTIVE_STATE_OBSERVER_H_
+#pragma once
+
+#include "chrome/test/base/ui_test_utils.h"
+
+class Panel;
+
+// Custom notification observer for waiting on panel active state.
+// Modeled after ui_test_utils notification observers.
+class PanelActiveStateObserver : public content::NotificationObserver {
+ public:
+  // Register to listen for panel active state change notifications
+  // for the specified panel to detect a change to the expected active
+  // state.
+  PanelActiveStateObserver(Panel* panel, bool expect_active);
+  virtual ~PanelActiveStateObserver();
+
+  // Wait until the active state has changed to the expected state.
+  void Wait();
+
+  // content::NotificationObserver:
+  virtual void Observe(int type,
+                       const content::NotificationSource& source,
+                       const content::NotificationDetails& details) OVERRIDE;
+
+ private:
+  bool AtExpectedState();
+  Panel* panel_;
+  bool expect_active_;
+  bool seen_;  // true after transition to expected state has been seen
+  bool running_;  // indicates whether message loop is running
+  content::NotificationRegistrar registrar_;
+  scoped_refptr<ui_test_utils::MessageLoopRunner> message_loop_runner_;
+
+  DISALLOW_COPY_AND_ASSIGN(PanelActiveStateObserver);
+};
+
+#endif  // CHROME_BROWSER_UI_PANELS_TEST_PANEL_ACTIVE_STATE_OBSERVER_H_