Merged op dispatch in OpReorderer

bug:22480459

Also switches std::functions to function pointers on OpReorderer, and
switches AssetAtlas' entry getter methods to using pixelRef pointers,
so it's clear they're the keys.

Change-Id: I3040ce5ff4e178a8364e0fd7ab0876ada7d4de05
diff --git a/libs/hwui/VertexBuffer.h b/libs/hwui/VertexBuffer.h
index c0373ac..bdb5b7b 100644
--- a/libs/hwui/VertexBuffer.h
+++ b/libs/hwui/VertexBuffer.h
@@ -118,7 +118,7 @@
         TYPE* end = current + vertexCount;
         mBounds.set(current->x, current->y, current->x, current->y);
         for (; current < end; current++) {
-            mBounds.expandToCoverVertex(current->x, current->y);
+            mBounds.expandToCover(current->x, current->y);
         }
     }