Fix potential synchronization issue in bitmap pool

Bug: 9072712

Change-Id: I7fcecd6ec63e461e06a6565519be6d86e3246155
diff --git a/src/com/android/photos/data/GalleryBitmapPool.java b/src/com/android/photos/data/GalleryBitmapPool.java
index a5a17ed..aca3e4b 100644
--- a/src/com/android/photos/data/GalleryBitmapPool.java
+++ b/src/com/android/photos/data/GalleryBitmapPool.java
@@ -19,7 +19,7 @@
 import android.graphics.Bitmap;
 import android.graphics.Point;
 import android.util.Pools.Pool;
-import android.util.Pools.SimplePool;
+import android.util.Pools.SynchronizedPool;
 
 import com.android.photos.data.SparseArrayBitmapPool.Node;
 
@@ -36,7 +36,7 @@
 
     private int mCapacityBytes;
     private SparseArrayBitmapPool [] mPools;
-    private Pool<Node> mSharedNodePool = new SimplePool<Node>(128);
+    private Pool<Node> mSharedNodePool = new SynchronizedPool<Node>(128);
 
     private GalleryBitmapPool(int capacityBytes) {
         mPools = new SparseArrayBitmapPool[3];