Add support code to test the cast system tray item.

ash/system/cast/tray_cast.h

Index: ash/system/cast/tray_cast.h
diff --git a/ash/system/cast/tray_cast.h b/ash/system/cast/tray_cast.h
index 04a4bc28a802aebee55c40818e4a36ed0e16a31e..4c1c40347f104d741e7760b223d4fe969c6d7926 100644
--- a/ash/system/cast/tray_cast.h
+++ b/ash/system/cast/tray_cast.h
@@ -5,6 +5,7 @@
 #ifndef ASH_SYSTEM_CAST_TRAY_CAST_H_
 #define ASH_SYSTEM_CAST_TRAY_CAST_H_
 
+#include "ash/ash_export.h"
 #include "ash/cast_config_delegate.h"
 #include "ash/shell_observer.h"
 #include "ash/system/tray/system_tray_item.h"
@@ -18,11 +19,20 @@ class CastDetailedView;
 class CastDuplexView;
 }  // namespace tray
 
-class TrayCast : public SystemTrayItem, public ShellObserver {
+class ASH_EXPORT TrayCast : public SystemTrayItem, public ShellObserver {
  public:
   explicit TrayCast(SystemTray* system_tray);
   ~TrayCast() override;
 
+  // The following are functions used for testing. It would be great if they

[achuithb, 2015/07/08 21:45:57]

Have you looked at FRIEND_TEST_ALL_PREFIXES?

[jdufault, 2015/07/09 23:11:28]

Doesn't seem to work, since the test and this class are in different compilation
modules.

+  // were private, but they are used in browsertests, which are implemented as
+  // derived classes, which means we cannot use friendship.
+  bool IsTrayInitializedForTest();

[achuithb, 2015/07/08 21:45:57]

const

[jdufault, 2015/07/09 23:11:28]

Done.

+  bool IsTrayVisibleForTest();

[achuithb, 2015/07/08 21:45:57]

const

[jdufault, 2015/07/09 23:11:28]

Done.

+  // Start a new cast to the given receiver.
+  void StartCastForTest(std::string id);

[achuithb, 2015/07/08 21:45:57]

const std::string& receiver_id

[jdufault, 2015/07/09 23:11:28]

Done.

+  void StopCastForTest();
+
  private:
   // Overridden from SystemTrayItem.
   views::View* CreateTrayView(user::LoginStatus status) override;