Fix the issue the setting crashes after unmount SD card in landscape

When rotate the phone, mLastClickedMountToggle and mClickedMountPoint
would be destroied which made dialog access NULL pointer.

Change-Id: Ic96fce93828ca7a6f8749fad6a258eb47831e062
Author: Chuanxiao Dong <chuanxiao.dong@intel.com>
Signed-off-by: Xiaokang Qin <xiaokang.qin@intel.com>
Signed-off-by: Bruce Beare <bruce.j.beare@intel.com>
Signed-off-by: Jack Ren <jack.ren@intel.com>
Author-tracking-BZ: 26569
diff --git a/src/com/android/settings/deviceinfo/Memory.java b/src/com/android/settings/deviceinfo/Memory.java
index cb344bf..cabc6e9 100644
--- a/src/com/android/settings/deviceinfo/Memory.java
+++ b/src/com/android/settings/deviceinfo/Memory.java
@@ -57,8 +57,8 @@
     // The mountToggle Preference that has last been clicked.
     // Assumes no two successive unmount event on 2 different volumes are performed before the first
     // one's preference is disabled
-    private Preference mLastClickedMountToggle;
-    private String mClickedMountPoint;
+    private static Preference mLastClickedMountToggle;
+    private static String mClickedMountPoint;
 
     // Access using getMountService()
     private IMountService mMountService = null;