Add thumb pool the cache Bitmap used for thumbnails.

Change-Id: Ib710f2a6fc1aa86fe4abdd18d1fa7ac71396a3b4
diff --git a/src/com/android/gallery3d/app/AbstractGalleryActivity.java b/src/com/android/gallery3d/app/AbstractGalleryActivity.java
index eddaea5..00f6ac5 100644
--- a/src/com/android/gallery3d/app/AbstractGalleryActivity.java
+++ b/src/com/android/gallery3d/app/AbstractGalleryActivity.java
@@ -178,6 +178,7 @@
             mGLRootView.unlockRenderThread();
         }
         MediaItem.getMicroThumbPool().clear();
+        MediaItem.getThumbPool().clear();
         MediaItem.getBytesBufferPool().clear();
     }