Move GenerationCache to the utils directory.

Change-Id: I210ffa8f1d76a102bb7d971c649c20a74d03fbe6
diff --git a/libs/hwui/PatchCache.cpp b/libs/hwui/PatchCache.cpp
index 4dc1a4d..eca5e4d 100644
--- a/libs/hwui/PatchCache.cpp
+++ b/libs/hwui/PatchCache.cpp
@@ -73,8 +73,8 @@
                 pixelWidth, pixelHeight, xDivs, yDivs, width, height);
 
         if (mCache.size() >= mMaxEntries) {
-            delete mCache.valueAt(0);
-            mCache.removeItemsAt(0, 1);
+            delete mCache.valueAt(mCache.size() - 1);
+            mCache.removeItemsAt(mCache.size() - 1, 1);
         }
 
         mCache.add(description, mesh);